WorldWideScience

Sample records for blue galaxies disks

  1. Blue E/S0 galaxies: merger remnants or disk rebuilding galaxies?

    CERN Document Server

    López-Aguerri, J A; Tresse, L

    2009-01-01

    Morphological early-type galaxies residing in the blue cloud (\\emph{blue E/S0s}) could be nice laboratories to understand the physical processes that provoke galaxy migrations in the color-mas space. We define blue E/S0 galaxies as objects having a clear early-type morphology on the HST/ACS images but with a blue rest-frame color. We isolate this way 210 $I_{AB}10^{10}$ in the COSMOS field located in three redshift bins ($0.2blue E/S0 resemble to merger remnants probably migrating to the red-sequence in a time-scale of $\\sim 3$ Gyr. Below this mass, they seem to be closer to normal late-type galaxies as if they were the result of minor mergers which triggered the central star-formation or were rebuilding a disk from the surrounding gas in a much longer time-scale, suggesting that they are moving back or staying in the blue-cloud.

  2. Galaxy Disks

    CERN Document Server

    van der Kruit, P C

    2011-01-01

    The formation and evolution of galactic disks is particularly important for understanding how galaxies form and evolve, and the cause of the variety in which they appear to us. Ongoing large surveys, made possible by new instrumentation at wavelengths from the ultraviolet (GALEX), via optical (HST and large groundbased telescopes) and infrared (Spitzer) to the radio are providing much new information about disk galaxies over a wide range of redshift. Although progress has been made, the dynamics and structure of stellar disks, including their truncations, are still not well understood. We do now have plausible estimates of disk mass-to-light ratios, and estimates of Toomre's $Q$ parameter show that they are just locally stable. Disks are mostly very flat and sometimes very thin, and have a range in surface brightness from canonical disks with a central surface brightness of about 21.5 $B$-mag arcsec$^{-2}$ down to very low surface brightnesses. It appears that galaxy disks are not maximal, except possibly in ...

  3. Galaxy Disks are Submaximal

    NARCIS (Netherlands)

    Bershady, Matthew A.; Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Andersen, David R.; Swaters, Rob A.

    2011-01-01

    We measure the contribution of galaxy disks to the overall gravitational potential of 30 nearly face-on intermediate-to-late-type spirals from the DiskMass Survey. The central vertical velocity dispersion of the disk stars (sigma(disk)(z,R=0)) is related to the maximum rotation speed (V-max) as sigm

  4. The Frequency of Field Blue-Straggler Stars in the Thick Disk and Halo System of the Galaxy

    CERN Document Server

    Santucci, Rafael M; Rossi, Silvia; Beers, Timothy C; Reggiani, Henrique M; Lee, Young Sun; Xue, Xiang-Xiang; Carollo, Daniela

    2015-01-01

    We present an analysis of a new, large sample of field blue-straggler stars (BSSs) in the thick disk and halo system of the Galaxy, based on stellar spectra obtained during the Sloan Digital Sky Survey (SDSS) and the Sloan Extension for Galactic Understanding and Exploration (SEGUE). Using estimates of stellar atmospheric parameters obtained from application of the SEGUE Stellar Parameter Pipeline, we obtain a sample of some 8000 BSSs, which are considered along with a previously selected sample of some 4800 blue horizontal-branch (BHB) stars. We derive the ratio of BSSs to BHB stars, F$_{\\rm BSS/BHB}$, as a function of Galactocentric distance and distance from the Galactic plane. The maximum value found for F$_{\\rm BSS/BHB}$ is $\\sim~$4.0 in the thick disk (at 3 kpc $<$ $|$Z$|$ $<$ 4 kpc), declining to on the order of $\\sim~1.5-2.0$ in the inner-halo region; this ratio continues to decline to $\\sim~$1.0 in the outer-halo region. We associate a minority of field BSSs with a likely extragalactic origin; ...

  5. Faint Blue Galaxies

    CERN Document Server

    Ellis, Richard S

    1997-01-01

    The physical properties of the faint blue galaxy population are reviewed in the context of observational progress made via deep spectroscopic surveys and Hubble Space Telescope imaging of field galaxies at various limits, and theoretical models for the integrated star formation history of the Universe. Notwithstanding uncertainties in the properties of the local population of galaxies, convincing evidence has emerged from several independent studies for a rapid decline in the volume-averaged star formation rate of field galaxies since a redshift z~1. Together with the small angular sizes and modest mean redshift of the faintest detectable sources, these results can be understood in hierarchical models where the bulk of the star formation occurred at redshifts between z~1-2. The physical processes responsible for the subsequent demise of the faint blue galaxy population remains unclear. Considerable progress will be possible when the evolutionary trends can be monitored in the context of independent physical p...

  6. Secular Evolution in Disk Galaxies

    CERN Document Server

    Kormendy, John

    2013-01-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via available evolution processes. The inner parts shrink and the outer parts expand, provided that some physical process transports energy or angular momentum outward. The evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks, and galaxy disks are all fundamentally similar. These processes for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. Part 1 discusses formation, growth, and death of bars. Part 2 details the slow ("secular") rearrangement of angular momentum that results from interactions between stars or gas and nonaxisymmetries such as bars. We have a heuristic understanding of how this forms outer rings, inner rings, and stuff dumped into the center. Observations show that barred galaxies have central concentrations of gas and star formation. Timescales imply that they grow central "pseudobulges" that get mistaken for ellip...

  7. Secular Evolution in Disk Galaxies

    Science.gov (United States)

    Kormendy, John

    2013-10-01

    Self-gravitating systems evolve toward the most tightly bound configuration that is reachable via the evolution processes that are available to them. They do this by spreading -- the inner parts shrink while the outer parts expand -- provided that some physical process efficiently transports energy or angular momentum outward. The reason is that self-gravitating systems have negative specific heats. As a result, the evolution of stars, star clusters, protostellar and protoplanetary disks, black hole accretion disks and galaxy disks are fundamentally similar. How evolution proceeds then depends on the evolution processes that are available to each kind of self-gravitating system. These processes and their consequences for galaxy disks are the subjects of my lectures and of this Canary Islands Winter School. I begin with a review of the formation, growth and death of bars. Then I review the slow (`secular') rearrangement of energy, angular momentum, and mass that results from interactions between stars or gas clouds and collective phenomena such as bars, oval disks, spiral structure and triaxial dark haloes. The `existence-proof' phase of this work is largely over: we have a good heuristic understanding of how nonaxisymmetric structures rearrange disk gas into outer rings, inner rings and stuff dumped onto the centre. The results of simulations correspond closely to the morphology of barred and oval galaxies. Gas that is transported to small radii reaches high densities. Observations confirm that many barred and oval galaxies have dense central concentrations of gas and star formation. The result is to grow, on timescales of a few Gyr, dense central components that are frequently mistaken for classical (elliptical-galaxy-like) bulges but that were grown slowly out of the disk (not made rapidly by major mergers). The resulting picture of secular galaxy evolution accounts for the richness observed in galaxy structure. We can distinguish between classical and pseudo

  8. ECO and RESOLVE: Galaxy Disk Growth in Environmental Context

    CERN Document Server

    Moffett, Amanda J; Berlind, Andreas A; Eckert, Kathleen D; Stark, David V; Hendel, David; Norris, Mark A; Grogin, Norman A

    2015-01-01

    We study the relationships between galaxy environments and galaxy properties related to disk (re)growth, considering two highly complete samples that are approximately baryonic mass limited into the high-mass dwarf galaxy regime, the Environmental COntext (ECO) catalog (data release herein) and the B-semester region of the REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey. We quantify galaxy environments using both group identification and smoothed galaxy density field methods. We use by-eye and quantitative morphological classifications plus atomic gas content measurements and estimates. We find that blue early-type (E/S0) galaxies, gas-dominated galaxies, and UV-bright disk host galaxies all become distinctly more common below group halo mass ~10^11.5 Msun, implying that this low group halo mass regime may be a preferred regime for significant disk growth activity. We also find that blue early-type and blue late-type galaxies inhabit environments of similar group halo mass at fixed baryonic mass, con...

  9. A Search for Extended Ultraviolet Disk (XUV-disk) Galaxies in the Local Universe

    CERN Document Server

    Thilker, David A; Meurer, Gerhardt; de Paz, Armando Gil; Boissier, Samuel; Madore, Barry F; Boselli, Alessandro; Ferguson, Annette M N; Muńoz-Mateos, Juan Carlos; Madsen, Greg J; Hameed, Salman; Overzier, Roderik A; Forster, Karl; Friedman, Peter G; Martin, D Christopher; Morrissey, Patrick; Neff, Susan G; Schiminovich, David; Seibert, Mark; Small, Todd; Wyder, Ted K; Donas, Jose; Heckman, Timothy M; Lee, Young-Wook; Milliard, Bruno; Rich, R Michael; Szalay, A S; Welsh, Barry Y; Yi, Sukyoung K

    2007-01-01

    We have initiated a search for extended ultraviolet disk (XUV-disk) galaxies in the local universe. Herein, we compare GALEX UV and visible--NIR images of 189 nearby (D$<$40 Mpc) S0--Sm galaxies included in the GALEX Atlas of Nearby Galaxies and present the first catalogue of XUV-disk galaxies. We find that XUV-disk galaxies are surprisingly common but have varied relative (UV/optical) extent and morphology. Type~1 objects ($\\ga$20% incidence) have structured, UV-bright/optically-faint emission features in the outer disk, beyond the traditional star formation threshold. Type~2 XUV-disk galaxies ($\\sim$10% incidence) exhibit an exceptionally large, UV-bright/optically-low-surface-brightness (LSB) zone having blue $UV-K_s$ outside the effective extent of the inner, older stellar population, but not reaching extreme galactocentric distance. If the activity occuring in XUV-disks is episodic, a higher fraction of present-day spirals could be influenced by such outer disk star formation. Type~1 disks are associa...

  10. Why are some galaxy disks extremely thin?

    CERN Document Server

    Banerjee, Arunima

    2012-01-01

    Some low surface brightness galaxies are known to have extremely thin stellar disks with the vertical to planar axes ratio 0.1 or less, often referred to as superthin disks. Although their existence is known for over three decades, the physical origin for the thin distribution is not understood. We model the stellar thickness for a two-component (gravitationally coupled stars and gas) disk embedded in a dark matter halo, for a superthin galaxy UGC 7321 which has a dense, compact halo, and compare with a typical dwarf galaxy HoII which has a non-compact halo. We show that while the presence of gas does constrain the disk thickness, it is the compact dark matter halo which plays the decisive role in determining the superthin disk distribution in low-mass disks. Thus the compact dark matter halo significantly affects the disk structure and this could be important for the early evolution of galaxies.

  11. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    Science.gov (United States)

    Watkins, Aaron E.; Mihos, J. Christopher; Harding, Paul

    2016-07-01

    We present results from deep, wide-field surface photometry of three nearby (D = 4-7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches a limiting surface brightness of {μ }B ˜ 28-30 mag arcsec-2 and probes colors down to {μ }B ˜ 27.5 mag arcsec-2. We compare our broadband optical data to available ultraviolet and high column density H i data to better constrain the star-forming history and stellar populations of the outermost parts of each galaxy’s disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies’ outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarity in outer disk properties despite each galaxy showing distinct levels of environmental influence, from a purely isolated galaxy (M94) to one experiencing weak tidal perturbations from its satellite galaxies (M106) to a galaxy recovering from a recent merger (M64), suggesting that a variety of evolutionary histories can yield similar outer disk structure. While this suggests a common secular mechanism for outer disk formation, the large extent of these smooth, red stellar populations—which reach several disk scale lengths beyond the galaxies’ spiral structure—may challenge models of radial migration given the lack of any nonaxisymmetric forcing at such large radii.

  12. Counterrotating Stars in Simulated Galaxy Disks

    CERN Document Server

    Algorry, David G; Abadi, Mario G; Sales, Laura V; Steinmetz, Matthias; Piontek, Franziska

    2013-01-01

    Counterrotating stars in disk galaxies are a puzzling dynamical feature whose origin has been ascribed to either satellite accretion events or to disk instabilities triggered by deviations from axisymmetry. We use a cosmological simulation of the formation of a disk galaxy to show that counterrotating stellar disk components may arise naturally in hierarchically-clustering scenarios even in the absence of merging. The simulated disk galaxy consists of two coplanar, overlapping stellar components with opposite spins: an inner counterrotating bar-like structure made up mostly of old stars surrounded by an extended, rotationally-supported disk of younger stars. The opposite-spin components originate from material accreted from two distinct filamentary structures which at turn around, when their net spin is acquired, intersect delineating a "V"-like structure. Each filament torques the other in opposite directions; the filament that first drains into the galaxy forms the inner counterrotating bar, while material ...

  13. The Red and Featureless Outer Disks of Nearby Spiral Galaxies

    CERN Document Server

    Watkins, Aaron E; Harding, Paul

    2016-01-01

    We present results from deep, wide-field surface photometry of three nearby (D=4--7 Mpc) spiral galaxies: M94 (NGC 4736), M64 (NGC 4826), and M106 (NGC 4258). Our imaging reaches limiting surface brightnesses of $\\mu_{B} \\sim$ 28 -- 30 mag arcsec$^{-2}$ and probes colors down to $\\mu_{B} \\sim$ 27.5 mag arcsec$^{-2}$. We compare our broadband optical data to available ultraviolet and high column-density HI data to better constrain the star forming history and stellar populations of the outermost parts of each galaxy's disk. Each galaxy has a well-defined radius beyond which little star formation occurs and the disk light appears both azimuthally smooth and red in color, suggestive of old, well-mixed stellar populations. Given the lack of ongoing star formation or blue stellar populations in these galaxies' outer disks, the most likely mechanisms for their formation are dynamical processes such as disk heating or radial migration, rather than inside-out growth of the disks. This is also implied by the similarit...

  14. Galaxy And Mass Assembly (GAMA): the Stellar Mass Budget of Galaxy Spheroids and Disks

    CERN Document Server

    Moffett, Amanda J; Driver, Simon P; Robotham, Aaron S G; Kelvin, Lee S; Alpaslan, Mehmet; Andrews, Stephen K; Bland-Hawthorn, Joss; Brough, Sarah; Cluver, Michelle E; Colless, Matthew; Davies, Luke J M; Holwerda, Benne W; Hopkins, Andrew M; Kafle, Prajwal R; Liske, Jochen; Meyer, Martin

    2016-01-01

    We build on a recent photometric decomposition analysis of 7506 Galaxy and Mass Assembly (GAMA) survey galaxies to derive stellar mass function fits to individual spheroid and disk component populations down to a lower mass limit of log(M_*/M_sun)= 8. We find that the spheroid/disk mass distributions for individual galaxy morphological types are well described by single Schechter function forms. We derive estimates of the total stellar mass densities in spheroids (rho_spheroid = 1.24+/-0.49 * 10^8 M_sun Mpc^-3 h_0.7) and disks (rho_disk = 1.20+/-0.45 * 10^8 M_sun Mpc^-3 h_0.7), which translates to approximately 50% of the local stellar mass density in spheroids and 48% in disks. The remaining stellar mass is found in the dwarf "little blue spheroid" class, which is not obviously similar in structure to either classical spheroid or disk populations. We also examine the variation of component mass ratios across galaxy mass and group halo mass regimes, finding the transition from spheroid to disk mass dominance ...

  15. Dynamical Stability and Galaxy Evolution in LSB Disk Galaxies

    OpenAIRE

    Mihos,C; McGaugh, S. S.; Blok, E.

    1996-01-01

    Published in: AIP Conf. Proc. 393 (1997) , pp.311 citations recorded in [Science Citation Index] Abstract: We demonstrate that, due to their low surface mass density and large dark matter content, LSB disks are quite stable against the growth of global bar modes. However, they may be only marginally stable against local disk instabilities. We simulate a collision between an LSB and HSB galaxy and find that, while the HSB galaxy forms a strong bar, the response of the LSB disk is milder, in th...

  16. Giant disk galaxies : Where environment trumps mass in galaxy evolution

    CERN Document Server

    Courtois, H M; Sorce, J G; Pomarede, D

    2015-01-01

    We identify some of the most HI massive and fastest rotating disk galaxies in the local universe with the aim of probing the processes that drive the formation of these extreme disk galaxies. By combining data from the Cosmic Flows project, which has consistently reanalyzed archival galaxy HI profiles, and 3.6$\\mu$m photometry obtained with the Spitzer Space Telescope, with which we can measure stellar mass, we use the baryonic Tully-Fisher (BTF) relationship to explore whether these massive galaxies are distinct. We discuss several results, but the most striking is the systematic offset of the HI-massive sample above the BTF. These galaxies have both more gas and more stars in their disks than the typical disk galaxy of similar rotational velocity. The "condensed" baryon fraction, $f_C$, the fraction of the baryons in a dark matter halo that settle either as cold gas or stars into the disk, is twice as high in the HI-massive sample than typical, and almost reaches the universal baryon fraction in some cases,...

  17. Extended HI disks in nearby spiral galaxies

    Science.gov (United States)

    Bosma, Albert

    2017-03-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a ``tilted ring model'' allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  18. Extended HI disks in nearby spiral galaxies

    CERN Document Server

    Bosma, A

    2016-01-01

    In this short write-up, I will concentrate on a few topics of interest. In the 1970s I found very extended HI disks in galaxies such as NGC 5055 and NGC 2841, out to 2 - 2.5 times the Holmberg radius. Since these galaxies are warped, a "tilted ring model" allows rotation curves to be derived, and evidence for dark matter to be found. The evaluation of the amount of dark matter is hampered by a disk-halo degeneracy, which can possibly be broken by observations of velocity dispersions in both the MgI region and the CaII region.

  19. POLAR DISK GALAXY FOUND IN WALL BETWEEN VOIDS

    NARCIS (Netherlands)

    Stanonik, K.; Platen, E.; Aragon-Calvo, M. A.; van Gorkom, J. H.; van de Weygaert, R.; van der Hulst, J. M.; Peebles, P. J. E.

    2009-01-01

    We have found an isolated polar disk galaxy in what appears to be a cosmological wall situated between two voids. This void galaxy is unique as its polar disk was discovered serendipitously in an Hi survey of SDSS void galaxies, with no optical counterpart to the Hi polar disk. Yet the Hi mass in th

  20. The Blue Straggler Population in Dwarf Galaxies

    CERN Document Server

    Momany, Yazan

    2014-01-01

    In this chapter I review the recent developments regarding the study of Blue Stragglers (BSS) in dwarf galaxies. The loose density environment of dwarf galaxies resembles that of the Galactic Halo, hence it is natural to compare their common BSS properties. At the same time, it is unescapable to compare with the BSS properties in Galactic Globular clusters, which constitute the reference point for BSS studies. Admittedly, the literature on BSS in dwarf galaxies is not plentiful. The limitation is mostly due to the large distance to even the closest dwarf galaxies. Nevertheless, recent studies have allowed a deeper insight on the BSS photometric properties that are worth examining.

  1. Galaxy Zoo Hubble: First results of the redshift evolution of disk fraction in the red sequence

    Science.gov (United States)

    Galloway, Melanie; Willett, Kyle; Fortson, Lucy; Scarlata, Claudia; Beck, Melanie; Masters, Karen; Melvin, Tom

    2016-01-01

    The transition of galaxies from the blue cloud to the red sequence is commonly linked to a morphological transformation from disk to elliptical structure. However, the correlation between color and morphology is not one-to-one, as evidenced by the existence of a significant population of red disks. As this stage in a galaxy's evolution is likely to be transitory, the mechanism by which red disks are formed offers insight to the processes that trigger quenching of star formation and the galaxy's position on the star-forming sequence. To study the population of disk galaxies in the red sequence as a function of cosmic time, we utilize data from the Galaxy Zoo: Hubble project, which uses crowdsourced visual classifications of images of galaxies selected from the AEGIS, COSMOS, GEMS, and GOODS surveys. We construct a large sample of over 10,000 disk galaxies spanning a wide (0 < z < 1.0) redshift range. We use this sample to examine the change in the fraction of disks in the red sequence with respect to all disks from z˜1 to the present day. Preliminary results confirm that the fraction of disks in the red sequence decreases as the Universe evolves. We discuss the quenching processes which may explain this trend, and which morphological transformations are most affected by it.

  2. Dynamics of Disk Galaxies and Their Satellites

    Directory of Open Access Journals (Sweden)

    Héctor Velázquez

    2001-01-01

    Full Text Available We address the heating and survival of galaxy disks by infalling satellites using self-consistent N-body simulations. We consider satellites with a variety of internal structures as well several orbits with different eccentricities and orientations. Also, the role of the central region of the galaxy (through a bulge is studied. We found that the analytical results of Toth & Ostriker (1992 overestimate the heating and thickening of the disk by a factor of 2-3. In particular, we found disks are more robust to the accretion of massive satellites (MS ~ 0.2 MD that follow retrograte orbits. Finally, the importance of the responsiveness of the halo is analized.

  3. Possible Local Spiral Counterparts to Compact Blue Galaxies at Intermediate Redshift

    CERN Document Server

    Barton, E J; Barton, Elizabeth J.; Zee, Liese van

    2001-01-01

    We identify nearby disk galaxies with optical structural parameters similar to those of intermediate-redshift compact blue galaxies. By comparing HI and optical emission-line widths, we show that the optical widths substantially underestimate the true kinematic widths of the local galaxies. By analogy, optical emission-line widths may underrepresent the masses of intermediate-z compact objects. For the nearby galaxies, the compact blue morphology is the result of tidally-triggered central star formation: we argue that interactions and minor mergers may cause apparently compact morphology at higher redshift.

  4. Young circumnuclear disks in elliptical galaxies

    Science.gov (United States)

    Sil'Chenko, Olga K.

    2009-04-01

    By means of integral-field spectroscopy with the Multi-Pupil Field/Fiber Spectrograph of the Russian 6-m telescope we have studied the central parts of NGC 759 and NGC 83— regular (non-interacting, without strong nuclear activity) round red luminous ( M B =-20.8--21.6) elliptical galaxies which are however known to possess molecular gas. In both galaxies we have found central stellar disks with the extension of 1-2 kpc along the radius which are evidently being formed just now.

  5. Cold Gas in Blue-Sequence E/S0s: Galaxies in Transition

    CERN Document Server

    Wei, Lisa H; Vogel, Stuart N; Baker, Andrew J

    2009-01-01

    We examine the HI+H_2 content of blue-sequence E/S0s -- a recently identified population of galaxies that are morphologically early type, but reside alongside spiral galaxies in color vs. stellar mass space. We test the idea that the majority of low-to-intermediate mass blue-sequence E/S0s may be settled products of past mergers evolving toward later-type morphology via disk regrowth. We find that blue-sequence E/S0s with stellar masses 1.0, comparable to those of spiral galaxies. Preliminary CO(1-0) maps reveal disk-like rotation of molecular gas in the inner regions of several of our blue-sequence E/S0s, which suggests that they may have gas disks suitable for stellar disk regrowth. At the current rate of star formation, many of our blue-sequence E/S0s will exhaust their atomic gas reservoirs in <~ 3 Gyr. Over the same time period, most of these galaxies are capable of substantial growth in the stellar component. Star formation in blue-sequence E/S0s appears to be bursty, and likely involves inflow trig...

  6. Blue diffuse dwarf galaxies: a clearer picture

    Science.gov (United States)

    James, Bethan L.; Koposov, Sergey E.; Stark, Daniel P.; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W.; McQuinn, Kristen B. W.

    2017-03-01

    The search for chemically unevolved galaxies remains prevalent in the nearby Universe, mostly because these systems provide excellent proxies for exploring in detail the physics of high-z systems. The most promising candidates are extremely metal-poor galaxies (XMPs), i.e. galaxies with population. In 2014, we reoriented this search using only morphological properties and uncovered a population of ∼150 'blue diffuse dwarf (BDD) galaxies', and published a sub-sample of 12 BDD spectra. Here, we present optical spectroscopic observations of a larger sample of 51 BDDs, along with their Sloan Digital Sky Survey (SDSS) photometric properties. With our improved statistics, we use direct-method abundances to confirm that BDDs are chemically unevolved (7.43 population synthesis models and estimated to be in the range log (M*/M⊙) ≃ 5-9. Unlike other low-metallicity star-forming galaxies, BDDs are in agreement with the mass-metallicity relation at low masses, suggesting that they are not accreting large amounts of pristine gas relative to their stellar mass. BDD galaxies appear to be a population of actively star-forming dwarf irregular (dIrr) galaxies which fall within the class of low-surface-brightness dIrr galaxies. Their ongoing star formation and irregular morphology make them excellent analogues for galaxies in the early Universe.

  7. The 2X-HI disks of spiral galaxies

    CERN Document Server

    Koribalski, B S

    2016-01-01

    The outskirts of galaxies - especially the very extended HI disks of galaxies - are strongly affected by their local environment. I highlight the giant 2X-HI disks of nearby galaxies (M 83, NGC 3621, and NGC 1512), studied as part of the Local Volume HI Survey (LVHIS), their kinematics and relation to XUV disks, signatures of tidal interactions and accretion events, the MHI - DHI relation as well as the formation of tidal dwarf galaxies. - Using multi-wavelength data, I create 3D visualisations of the gas and stars in galaxies, with the shape of their warped disks obtained through kinematic modelling of their HI velocity fields.

  8. Blue straggler stars in dwarf spheroidal galaxies

    NARCIS (Netherlands)

    Mapelli, M.; Ripamonti, E.; Tolstoy, E.; Sigurdsson, S.; Irwin, M. J.; Battaglia, G.

    2007-01-01

    Blue straggler star (BSS) candidates have been observed in all old dwarf spheroidal galaxies (dSphs), however whether or not they are authentic BSSs or young stars has been a point of debate. To both address this issue and obtain a better understanding of the formation of BSSs in different environme

  9. Forming Disk Galaxies in Lambda CDM Simulations

    CERN Document Server

    Governato, F; Mayer, L; Quinn, T; Stinson, G; Valenzuela, O; Wadsley, J; Willman, B

    2006-01-01

    We used fully cosmological, high resolution N-body + SPH simulations to follow the formation of disk galaxies with rotational velocities between 135 and 270 km/sec in a Lambda CDM universe. The simulations include gas cooling, star formation, the effects of a uniform UV background and a physically motivated description of feedback from supernovae. The host dark matter halos have a spin and last major merger redshift typical of galaxy sized halos as measured in recent large scale N--Body simulations. The simulated galaxies form rotationally supported disks with realistic exponential scale lengths and fall on both the I-band and baryonic Tully Fisher relations. An extended stellar disk forms inside the Milky Way sized halo immediately after the last major merger. The combination of UV background and SN feedback drastically reduces the number of visible satellites orbiting inside a Milky Way sized halo, bringing it in fair agreement with observations. Our simulations predict that the average age of a primary gal...

  10. Extended Light in E/S0 Galaxies and Implications for Disk Rebirth

    CERN Document Server

    Moffett, Amanda J; Laine, Seppo; Wei, Lisa H; Baker, Andrew J; Impey, Chris D

    2009-01-01

    The recent discovery of extended ultraviolet (XUV) disks around a large fraction of late-type galaxies provides evidence for unexpectedly large-scale disk building at recent epochs. Combining GALEX UV observations with deep optical and Spitzer IR imaging, we search for XUV disks in a sample of nearby low-to-intermediate mass E/S0 galaxies to explore evidence for disk rebuilding after mergers. Preliminary visual classification yields ten XUV-disk candidates from the full sample of 30, intriguingly similar to the ~30% frequency for late-type galaxies. These XUV candidates occur at a wide range of masses and on both the red and blue sequences in color vs. stellar mass, indicating a possible association with processes like gas accretion and/or galaxy interactions that would affect the galaxy population broadly. We go on to apply the quantitative Type 1 and Type 2 XUV-disk definitions to a nine-galaxy subsample analyzed in detail. For this subsample, six of the nine are Type 1 XUVs, i.e., galaxies with UV structur...

  11. The Stellar Structures around Disk Galaxies

    CERN Document Server

    Drozdovsky, I; Aparicio, A; Gallart, C; Monelli, M; Hidalgo, S; Bernard, E J; Galazutdinova, O

    2016-01-01

    We present a brief summary of our current results on the stellar distribution and population gradients of the resolved stars in the surroundings of ~50 nearby disk galaxies, observed with space- (Hubble & Spitzer) and ground-based telescopes (Subaru, VLT, BTA, Palomar, CFHT & INT). We examine the radial (in-plane) and vertical (extraplanar) distributions of resolved stars as a function of stellar age and metallicity by tracking changes in the color-magnitude diagram of face-on and edge-on galaxies. Our data show, that the scale length and height of a stellar population increases with age, with the oldest detected stellar populations identified at a large galactocentric radius or extraplanar height, out to typically a few kpc. In the most massive of the studied galaxies there is evidence for a break in number density and color gradients of evolved stars, which plausibly correspond to the thick disk and halo components of the galaxies. The ratio of intermediate-age to old stars in the outermost fields c...

  12. Star Formation Modes in Low-Mass Disk Galaxies

    CERN Document Server

    Gallagher, J S

    2001-01-01

    Low-mass disk galaxies with well-organized structures are relatively common in low density regions of the nearby Universe. They display a wide range in levels of star formation activity, extending from sluggishly evolving `superthin' disk systems to nearby starbursts. Investigations of this class of galaxy therefore provides opportunities to test and define models of galactic star formation processes. In this paper we briefly explore characteristics of examples of quiescent and starbursting low-mass disk galaxies.

  13. Do low surface brightness galaxies have dense disks?

    CERN Document Server

    Saburova, A S

    2010-01-01

    The disk masses of four low surface brightness galaxies (LSB) were estimated using marginal gravitational stability criterion and the stellar velocity dispersion data which were taken from Pizzella et al., 2008 [1]. The constructed mass models appear to be close to the models of maximal disk. The results show that the disks of LSB galaxies may be significantly more massive than it is usually accepted from their brightnesses. In this case their surface densities and masses appear to be rather typical for normal spirals. Otherwise, unlike the disks of many spiral galaxies, the LSB disks are dynamically overheated.

  14. Chemical Evolution of Blue Compact Galaxies

    Institute of Scientific and Technical Information of China (English)

    Fei Shi; Xu Kong; Fu-Zhen Cheng

    2006-01-01

    Based on a sample of 72 Blue Compact Galaxies (BCGs) observed with the 2.16 m telescope of the National Astronomical Observatories, Chinese Academy of Sciences (NAOC) and about 4000 strong emission line galaxies from the Sloan Digital Sky Survey,we analyzed their chemical evolution history using the revised chemical evolution model of Larsen et al. Our sample covers a much larger metallicity range (7.2<12+log(O/H) <9.0). We found that, in order to reproduce the observed abundance pattern and gas fraction over the whole metallicity range, a relatively continuous star formation history is needed for high metallicity galaxies, while assuming a series of instantaneous bursts with long quiescent periods (some Gyrs) for low metallicity galaxies. Model calculations also show that only the closed-box model is capable of reproducing the observational data over the whole metallicity range. Models that consider the ordinary winds and/or inflow can only fit the observations in the low metallicity range, and a model with enriched wind cannot fit the data in the whole metallicity range. This implies that the current adopted simple wind and inflow models are not applicable to massive galaxies, where the underlying physics of galactic winds or inflow could be more complicated.

  15. Blue diffuse dwarf galaxies: a clearer picture

    CERN Document Server

    James, Bethan L; Stark, Daniel P; Belokurov, Vasily; Pettini, Max; Olszewski, Edward W; McQuinn, Kristen B W

    2016-01-01

    The search for chemically unevolved galaxies remains prevalent in the nearby Universe, mostly because these systems provide excellent proxies for exploring in detail the physics of high-z systems. The most promising candidates are extremely metal-poor galaxies (XMPs), i.e., galaxies with <1/10 solar metallicity. However, due to the bright emission line based search criteria traditionally used to find XMPs, we may not be sampling the full XMP population. In 2014 we reoriented this search using only morphological properties and uncovered a population of ~150 `blue diffuse dwarf (BDD) galaxies', and published a sub-sample of 12 BDD spectra. Here we present optical spectroscopic observations of a larger sample of 51 BDDs, along with their SDSS photometric properties. With our improved statistics, we use direct-method abundances to confirm that BDDs are chemically unevolved (7.43<12+log(O/H)<8.01), with ~20% of our sample classified as being XMP galaxies, and find they are actively forming stars at rates ...

  16. STELLAR POPULATIONS AND RADIAL MIGRATIONS IN VIRGO DISK GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Roediger, Joel C.; Courteau, Stephane [Department of Physics, Engineering Physics and Astronomy, Queen' s University, Kingston, Ontario (Canada); Sanchez-Blazquez, Patricia [Deptartamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); McDonald, Michael, E-mail: jroediger@astro.queensu.ca, E-mail: courteau@astro.queensu.ca, E-mail: p.sanchezblazquez@uam.es, E-mail: mcdonald@space.mit.edu [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology Cambridge, MA (United States)

    2012-10-10

    We present new stellar age profiles, derived from well-resolved optical and near-infrared images of 64 Virgo cluster disk galaxies, whose analysis poses a challenge for current disk galaxy formation models. Our ability to break the age-metallicity degeneracy and the significant size of our sample represent key improvements over complementary studies of field disk galaxies. Our results can be summarized as follows: first, and contrary to observations of disk galaxies in the field, these cluster galaxies are distributed almost equally amongst the three main types of disk galaxy luminosity profiles (I/II/III), indicating that the formation and/or survival of Type II breaks is suppressed within the cluster environment. Second, we find examples of statistically significant inversions ({sup U}-shapes{sup )} in the age profiles of all three disk galaxy types, reminiscent of predictions from high-resolution simulations of classically truncated Type II disks in the field. These features characterize the age profiles for only about a third ({<=}36%) of each disk galaxy type in our sample. An even smaller fraction of cluster disks ({approx}11% of the total sample) exhibit age profiles that decrease outward (i.e., negative age gradients). Instead, flat and/or positive age gradients prevail ({>=}50%) within our Type I, II, and III subsamples. These observations thus suggest that while stellar migrations and inside-out growth can play a significant role in the evolution of all disk galaxy types, other factors contributing to the evolution of galaxies can overwhelm the predicted signatures of these processes. We interpret our observations through a scenario whereby Virgo cluster disk galaxies formed initially like their brethren in the field but which, upon falling into the cluster, were transformed into their present state through external processes linked to the environment (e.g., ram-pressure stripping and harassment). Current disk galaxy formation models, which have largely

  17. Mass Distribution and Bar Formation in Growing Disk Galaxy Models

    CERN Document Server

    Berrier, Joel C

    2016-01-01

    We report idealized simulations that mimic the growth of galaxy disks embedded in responsive halos and bulges. The disks manifested an almost overwhelming tendency to form strong bars that we found very difficult to prevent. We found that fresh bars formed in growing disks after we had destroyed the original, indicating that bar formation also afflicts continued galaxy evolution, and not just the early stages of disk formation. This behavior raises still more insistently the previously unsolved question of how some galaxies avoid bars. Since our simulations included only collisionless star and halo particles, our findings may apply to gas-poor galaxies only; however the conundrum persists for the substantial unbarred fraction of those galaxies. Our original objective was to study how internal dynamics rearranged the distribution of mass in the disk as a generalization of our earlier study with rigid spherical components. With difficulty, we were able to construct some models that were not strongly influenced ...

  18. Outer Disk Star Formation in HI selected Galaxies

    CERN Document Server

    Meurer, Gerhardt

    2016-01-01

    The HI in galaxies often extends past their conventionally defined optical extent. I report results from our team which has been probing low intensity star formation in outer disks using imaging in H-alpha and ultraviolet. Using a sample of hundreds of HI selected galaxies, we confirm that outer disk HII regions and extended UV disks are common. Hence outer disks are not dormant but are dimly forming stars. Although the ultraviolet light in galaxies is more centrally concentrated than the HI, the UV/HI ratio (the Star Formation Efficiency) is nearly constant, with a slight dependency on surface brightness. This result is well accounted for in a model where disks maintain a constant stability parameter Q. This model also accounts for how the ISM and star formation are distributed in the bright parts of galaxies, and how HI appears to trace the distribution of dark matter in galaxy outskirts.

  19. Near-Infrared Bulge-Disk Correlations of Lenticular Galaxies

    CERN Document Server

    Barway, Sudhanshu; Kembhavi, Ajit K; Mayya, Y D

    2008-01-01

    We consider the luminosity and environmental dependence of structural parameters of lenticular galaxies in the near-infrared K band. Using a two-dimensional galaxy image decomposition technique, we extract bulge and disk structural parameters for a sample of 36 lenticular galaxies observed by us in the K band. By combining data from the literature for field and cluster lenticulars with our data, we study correlations between parameters that characterise the bulge and the disk as a function of luminosity and environment. We find that scaling relations such as the Kormendy relation, photometric plane and other correlations involving bulge and disk parameters show a luminosity dependence. This dependence can be explained in terms of galaxy formation models in which faint lenticulars (M_T > -24.5) formed via secular formation processes that likely formed the pseudobulges of late-type disk galaxies, while brighter lenticulars (M_T < -24.5) formed through a different formation mechanism most likely involving maj...

  20. Are dusty galaxies blue? Insights on UV attenuation from dust-selected galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Casey, C. M.; Cooray, A. [Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697 (United States); Scoville, N. Z. [California Institute of Technology, 1216 East California Boulevard, Pasadena, CA 91125 (United States); Sanders, D. B.; Lee, N. [Institute for Astronomy, University of Hawai' i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Finkelstein, S. L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Capak, P. [Spitzer Science Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Conley, A. [Center for Astrophysics and Space Astronomy 389-UCB, University of Colorado, Boulder, CO 80309 (United States); De Zotti, G. [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 2, I-35122 Padova (Italy); Farrah, D. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Fu, H. [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52242 (United States); Le Floc' h, E. [CEA-Saclay, Orme des Merisiers, bât. 709, F-91191 Gif-sur-Yvette Cedex (France); Ilbert, O. [Aix Marseille Université, CNRS, Laboratoire d' Astrophysique de marseille, UMR 7326, F-13388 Marseille (France); Ivison, R. J. [Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ (United Kingdom); Takeuchi, T. T. [Nagoya University, Division of Particle and Astrophysical Science, Furo-cho, Chikusa-ku, Nagoya 464-8602 (Japan)

    2014-12-01

    Galaxies' rest-frame ultraviolet (UV) properties are often used to directly infer the degree to which dust obscuration affects the measurement of star formation rates (SFRs). While much recent work has focused on calibrating dust attenuation in galaxies selected at rest-frame ultraviolet wavelengths, locally and at high-z, here we investigate attenuation in dusty, star forming galaxies (DSFGs) selected at far-infrared wavelengths. By combining multiwavelength coverage across 0.15-500 μm in the COSMOS field, in particular making use of Herschel imaging, and a rich data set on local galaxies, we find an empirical variation in the relationship between the rest-frame UV slope (β) and the ratio of infrared-to-ultraviolet emission (L {sub IR}/L {sub UV} ≡ IRX) as a function of infrared luminosity, or total SFR. Both locally and at high-z, galaxies above SFR ≳ 50 M {sub ☉} yr{sup –1} deviate from the nominal IRX-β relation toward bluer colors by a factor proportional to their increasing IR luminosity. We also estimate contamination rates of DSFGs on high-z dropout searches of <<1% at z ≲ 4-10, providing independent verification that contamination from very dusty foreground galaxies is low in Lyman-break galaxy searches. Overall, our results are consistent with the physical interpretation that DSFGs, e.g., galaxies with >50 M {sub ☉} yr{sup –1}, are dominated at all epochs by short-lived, extreme burst events, producing many young O and B stars that are primarily, yet not entirely, enshrouded in thick dust cocoons. The blue rest-frame UV slopes of DSFGs are inconsistent with the suggestion that most DSFGs at z ∼ 2 exhibit steady-state star formation in secular disks.

  1. Bulges and disks in the local Universe. Linking the galaxy structure to star formation activity

    CERN Document Server

    Morselli, L; Erfanianfar, G; Concas, A

    2016-01-01

    Galaxy morphology and star formation activity are strictly linked, in the way that bulge-dominated galaxies are in general quiescent, while disk dominated galaxies are actively star-forming. In this paper, we study the properties of bulges and disks as a function of the position of galaxies in the star formation rate (SFR) - stellar mass ($M_{\\star}$) plane. Our sample is built on the SDSS DR7 catalogue, and the bulge-disk decomposition is the one of Simard et al. (2011). We find that at a given stellar mass the Main Sequence (MS) is populated by galaxies with the lowest B/T ratios. The B/T on the MS increases with increasing stellar mass, thus confirming previous results in literature. In the upper envelop of the MS, the average B/T is higher than that of MS counterparts at fixed stellar mass. This indicates that starburst galaxies have a significant bulge component. In addition, bulges above the MS are characterised by blue colours, whereas, if on the MS or below it, they are mostly red and dead. The disks ...

  2. THE PARKER INSTABILITY IN DISK GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, L. F. S.; Sarson, G. R.; Shukurov, A.; Bushby, P. J.; Fletcher, A., E-mail: luiz.rodrigues@newcastle.ac.uk, E-mail: graeme.sarson@newcastle.ac.uk, E-mail: anvar.shukurov@newcastle.ac.uk, E-mail: paul.bushby@newcastle.ac.uk, E-mail: andrew.fletcher@newcastle.ac.uk [School of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne, NE1 7RU (United Kingdom)

    2016-01-01

    We examine the evolution of the Parker instability in galactic disks using 3D numerical simulations. We consider a local Cartesian box section of a galactic disk, where gas, magnetic fields, and cosmic rays are all initially in a magnetohydrostatic equilibrium. This is done for different choices of initial cosmic-ray density and magnetic field. The growth rates and characteristic scales obtained from the models, as well as their dependences on the density of cosmic rays and magnetic fields, are in broad agreement with previous (linearized, ideal) analytical work. However, this nonideal instability develops a multimodal 3D structure, which cannot be quantitatively predicted from the earlier linearized studies. This 3D signature of the instability will be of importance in interpreting observations. As a preliminary step toward such interpretations, we calculate synthetic polarized intensity and Faraday rotation measure (RM) maps, and the associated structure functions of the latter, from our simulations; these suggest that the correlation scales inferred from RM maps are a possible probe for the cosmic-ray content of a given galaxy. Our calculations highlight the importance of cosmic rays in these measures, making them an essential ingredient of realistic models of the interstellar medium.

  3. Stellar and Gas Phase Metallicity of Low Surface Brighness Galaxies: Implication on Star Formation Process within Young Disk Galaxies

    Science.gov (United States)

    Kim, Ji Hoon

    2015-08-01

    Low surface brightness (LSB) galaxies, whose central surface brightness, μB, is fainter than 23 mag/arcsec2 in the B-band, have been one of the most intriguing galaxy populations. Their unique characteristics, such as blue colors in optical and near-infrared light, low metallicity, low stellar and gas surface densities, low dust content, and high gas mass fraction (up to 90%), resemble physical conditions of young galaxies of the early Universe whose interstellar medium (ISM) has not been enriched before major star formation activities initiated and should provide a testbed for star formation process at the exremly low surface density regime. Given that their star formation histories are still poorly constrained, LSB galaxies are known to have large specific star formation rates (sSFRs) with large gas fractions. There is also a correlation between their sSFRs and gas fractions. One of plausible scenarios is that the star formation efficiency may be an increasing funtion of time, perhaps due in part to the slow build up of metals and dust. Moreover, it is suspected that, being located in low number density area in terms of galaxy environment, LSB galaxies may receive additional gas to fuel their star formation activity via sporadic cold gas accretion, especially toward their outskirt regions analogous to extended ultraviolet disks. Due to their relatively isolated nature without having endured much interactions, LSB galaxies can mimic star formation processes of disk galaxies of the early Universe within their interstellar media (ISM). We present preliminary results based on stellar and gas phase metallicity of LSB galaxies along with their environment parameters to show how star-forming ISM of young disk galaxies before metal enrichment.

  4. Metallicity Gradients in Disks: Do Galaxies Form Inside-Out?

    CERN Document Server

    Pilkington, K; Gibson, B K; Calura, F; Michel-Dansac, L; Thacker, R J; Molla, M; Matteucci, F; Rahimi, A; Kawata, D; Kobayashi, C; Brook, C B; Stinson, G S; Couchman, H M P; Bailin, J; Wadsley, J

    2012-01-01

    We examine radial and vertical metallicity gradients using a suite of disk galaxy simulations, supplemented with two classic chemical evolution approaches. We determine the rate of change of gradient and reconcile differences between extant models and observations within the `inside-out' disk growth paradigm. A sample of 25 disks is used, consisting of 19 from our RaDES (Ramses Disk Environment Study) sample, realised with the adaptive mesh refinement code RAMSES. Four disks are selected from the MUGS (McMaster Unbiased Galaxy Simulations) sample, generated with the smoothed particle hydrodynamics (SPH) code GASOLINE, alongside disks from Rahimi et al. (GCD+) and Kobayashi & Nakasato (GRAPE-SPH). Two chemical evolution models of inside-out disk growth were employed to contrast the temporal evolution of their radial gradients with those of the simulations. We find that systematic differences exist between the predicted evolution of radial abundance gradients in the RaDES and chemical evolution models, comp...

  5. The effect of environment on the structure of disk galaxies

    CERN Document Server

    Pranger, Florian; Kelvin, Lee S; Cebrián, María

    2016-01-01

    We study the influence of environment on the structure of disk galaxies, using IMFIT to measure the g- and r-band parameters of the surface-brightness profiles for ~200 low-redshift (z<0.051) cluster and field disk-galaxies with intermediate stellar mass (10^10 M_sol < M_star < 4 x 10^10 M_sol) from the Sloan Digital Sky Survey, DR7. Based on this measurement, we assign each galaxy to a surface-brightness profile type (Type I single-exponential, Type II truncated, Type III anti-truncated). In addition, we measure (g-r) restframe colour for disk regions separated by the truncation radius. Cluster disk galaxies (at the same stellar mass) have redder (g-r) colour by ~0.2 mag than field galaxies. This reddening is the same inside and outside the break radius. Cluster disk galaxies are also more compact than field disks by 10%. This change is reflected in the outer scalelengths, which increase by ~10% in the cluster environment compared to the field. Finally, Type I galaxies are 3 times more frequent in t...

  6. Galaxy Zoo: CANDELS Barred Disks and Bar Fractions

    CERN Document Server

    Simmons, B D; Lintott, Chris; Masters, Karen L; Willett, Kyle W; Keel, William C; Smethurst, R J; Cheung, Edmond; Nichol, Robert C; Schawinski, Kevin; Rutkowski, Michael; Kartaltepe, Jeyhan S; Bell, Eric F; Casteels, Kevin R V; Conselice, Christopher J; Almaini, Omar; Ferguson, Henry C; Fortson, Lucy; Hartley, William; Kocevski, Dale; Koekemoer, Anton M; McIntosh, Daniel H; Mortlock, Alice; Newman, Jeffrey A; Ownsworth, Jamie; Bamford, Steven; Dahlen, Tomas; Faber, Sandra M; Finkelstein, Steven L; Fontana, Adriano; Galametz, Audrey; Grogin, N A; Grutzbauch, Ruth; Guo, Yicheng; Haussler, Boris; Jek, Kian J; Kaviraj, Sugata; Lucas, Ray A; Peth, Michael; Salvato, Mara; Wiklind, Tommy; Wuyts, Stijn

    2014-01-01

    The formation of bars in disk galaxies is a tracer of the dynamical maturity of the population. Previous studies have found that the incidence of bars in disks decreases from the local Universe to z ~ 1, and by z > 1 simulations predict that bar features in dynamically mature disks should be extremely rare. Here we report the discovery of strong barred structures in massive disk galaxies at z ~ 1.5 in deep rest-frame optical images from CANDELS. From within a sample of 876 disk galaxies identified by visual classification in Galaxy Zoo, we identify 123 barred galaxies. Selecting a sub-sample within the same region of the evolving galaxy luminosity function (brighter than L*), we find that the bar fraction across the redshift range 0.5< z < 2 (f_bar = 10.7 +6.3 -3.5% after correcting for incompleteness) does not significantly evolve. We discuss the implications of this discovery in the context of existing simulations and our current understanding of the way disk galaxies have evolved over the last 11 bil...

  7. Disk galaxy formation and evolution models up to intermediate redshifts

    CERN Document Server

    Firmani, C

    1999-01-01

    Making use of a seminumerical method we develop a scenario of disk galaxy formation and evolution in the framework of inflationary cold dark matter (CDM) cosmologies. Within the virializing dark matter halos, disks in centrifugal equilibrium are built-up and their galactic evolution is followed through an approach which considers the gravitational interactions among the galaxy components, the turbulence and energy balance of the ISM, the star formation (SF) process due to disk gravitational instabilities, the stellar evolution and the secular formation of a bulge. We find that the main properties and correlations of disk galaxies are determined by the mass, the hierarchical mass aggregation history and the primordial angular momentum. The models follow the same trends across the Hubble sequence than the observed galaxies. The predicted TF relation is in good agreement with the observations except for the standart CDM. While the slope of this relation remains almost constant up to intermediate redshifts, its z...

  8. First Evidence of Circumstellar Disks around Blue Straggler Stars

    CERN Document Server

    De Marco, O; Ouellette, J A; Zurek, D R; Shara, M M; Marco, Orsola De; Lanz, Thierry; Ouellette, John A.; Zurek, David; Shara, Michael M.

    2004-01-01

    We present an analysis of optical HST/STIS and HST/FOS spectroscopy of 6 blue stragglers found in the globular clusters M3, NGC6752 and NGC6397. These stars are a subsample of a set of ~50 blue stragglers and stars above the main sequence turn-off in four globular clusters which will be presented in an forthcoming paper. All but the 6 stars presented here can be well fitted with non-LTE model atmospheres. The 6 misfits, on the other hand, possess Balmer jumps which are too large for the effective temperatures implied by their Paschen continua. We find that our data for these stars are consistent with models only if we account for extra absorption of stellar Balmer photons by an ionized circumstellar disk. Column densities of HI and CaII are derived as are the the disks' thicknesses. This is the first time that a circumstellar disk is detected around blue stragglers. The presence of magnetically-locked disks attached to the stars has been suggested as a mechanism to lose the large angular momentum imparted by ...

  9. Simulations of magnetic fields in isolated disk galaxies

    CERN Document Server

    Pakmor, R

    2012-01-01

    Magnetic fields are known to be dynamically important in the interstellar medium of our own Galaxy, and they are ubiquitously observed in diffuse gas in the halos of galaxies and galaxy clusters. Yet, magnetic fields have typically been neglected in studies of the formation of galaxies, leaving their global influence on galaxy formation largely unclear. We extend our MHD implementation in the moving-mesh code Arepo to cosmological problems which include radiative cooling and the formation of stars. In particular, we replace our previously employed divergence cleaning approach with a Powell 8-wave scheme, which turns out to be significantly more stable, even in very dynamic environments. We verify the improved accuracy through simulations of the MRI in accretion disks, that reproduce its correct linear growth rate. Using this new MHD code, we simulate the formation of isolated disk galaxies similar to the Milky Way using idealized initial conditions with and without magnetic fields. We find that the magnetic f...

  10. The outer disks of early-type galaxies. I. Surface-brightness profiles of barred galaxies

    NARCIS (Netherlands)

    Erwin, Peter; Pohlen, Michael; Beckman, John E.

    2008-01-01

    We present a study of 66 barred, early-type (S0-Sb) disk galaxies, focused on the disk surface brightness profile outside the bar region, with the aim of throwing light on the nature of Freeman type I and II profiles, their origins, and their possible relation to disk truncations. This paper discuss

  11. The Morphology of Low Surface Brightness Disk Galaxies

    Science.gov (United States)

    McGaugh, S.; Schombert, J.; Bothun, G.

    1994-01-01

    Images of a sample of low surface brightness (LSB) disk galaxies are presented. These galaxies are generally late types; however, they are not dwarfs, being intrinsically large and luminous. The morphology of LSB galaxies is discussed in terms of the physical interpretation of the Hubble sequence, the stages of which are found to be nonlinear in the sense that smaller physical differences separate mid to early type spirals than late types.

  12. Bulge growth through disk instabilities in high-redshift galaxies

    CERN Document Server

    Bournaud, Frederic

    2015-01-01

    The role of disk instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disk galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges. This secular growth of bulges in modern disk galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudo-bulges at slow rates and with long star-formation timescales. Disk instabilities at high redshift (z>1) in moderate-mass to massive galaxies (10^10 to a few 10^11 Msun of stars) are very different from those found in modern spiral galaxies. High-redshift disks are globally unstable and fragment into giant clumps containing 10^8-10^9 Msun of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disk evolution and bulge growth through various mechanisms, on short timescales. The giant clumps can...

  13. The luminosity-diameter relation for disk galaxies in different environments

    Energy Technology Data Exchange (ETDEWEB)

    Girardi, M.; Biviano, A.; Giuricin, G.; Mardirossian, F.; Mezzetti, M. (Scuola Internazionale Superiore di Studi Avanzati, Trieste (Italy) Trieste Universita (Italy) Centro Interuniversitario Regionale di Astrofisica e Cosmologia, Trieste (Italy))

    1991-01-01

    Several samples of disk galaxies have been collected in order to study, in each of them, the relation between the blue total corrected absolute magnitude and the absolute corrected isophotal diameter. These luminosity-diameter relations have been compared to detect a possible dependence on the density of the galaxy environment. No significant differences have been found among the several relations, especially if selection criteria relative to the various samples are taken into account. This result is in disagreement with several previous claims. 61 refs.

  14. The Formation of Polar Disk Galaxies

    CERN Document Server

    Brook, Chris B; Quinn, Thomas; Wadsley, James; Brooks, Alyson M; Willman, Beth; Stilp, Adrienne; Jonsson, Patrik

    2008-01-01

    Polar Ring Galaxies, such as NGC4650A, are a class of galaxy which have two kinematically distinct components that are inclined by almost 90 degrees to each other. These striking galaxies challenge our understanding of how galaxies form; the origin of their distinct components has remained uncertain, and the subject of much debate. We use high-resolution cosmological simulations of galaxy formation to show that Polar Ring Galaxies are simply an extreme example of the angular moment misalignment that occurs during the hierarchical structure formation characteristic of Cold Dark Matter cosmology. In our model, Polar Ring Galaxies form through the continuous accretion of gas whose angular momentum is misaligned with the central galaxy.

  15. Tidally Induced Offset Disks in Magellanic Spiral Galaxies

    Science.gov (United States)

    Pardy, Stephen A.; D'Onghia, Elena; Athanassoula, E.; Wilcots, Eric M.; Sheth, Kartik

    2016-08-01

    Magellanic spiral galaxies are a class of one-armed systems that often exhibit an offset stellar bar and are rarely found around massive spiral galaxies. Using a set of N-body and hydrodynamic simulations, we consider a dwarf-dwarf galaxy interaction as the driving mechanism for the formation of this peculiar class of systems. We investigate here the relation between the dynamical, stellar, and gaseous disk center and the bar. In all our simulations the bar center always coincides with the dynamical center, while the stellar disk becomes highly asymmetric during the encounter, causing the photometric center of the Magellanic galaxy disk to become mismatched with both the bar and the dynamical center. The disk asymmetries persist for almost 2 Gyr, the time that it takes for the disk to be recentered with the bar, and well after the companion has passed. This explains the nature of the offset bar found in many Magellanic-type galaxies, including the Large Magellanic Cloud (LMC) and NGC 3906. In particular, these results, once applied to the LMC, suggest that the dynamical center should reside in the bar center instead of the H i center as previously assumed, pointing to a variation in the current estimate of the north component of the LMC proper motion.

  16. Metallicity evolution in mergers of disk galaxies with black holes

    Science.gov (United States)

    Rantala, Antti; Johansson, Peter H.

    2016-10-01

    We use the TreeSPH simulation code Gadget-3 including a recently improved smoothed particle hydrodynamics (SPH) module, a detailed metallicity evolution model and sophisticated subresolution feedback models for supernovae and supermassive black holes in order to study the metallicity evolution in disk galaxy mergers. In addition, we examine the simulated morphology, star formation histories, metallicity gradients and kinematic properties of merging galaxies and merger remnants. We will compare our simulation results with observations of the early-type Centaurus A galaxy and the currently colliding Antennae galaxies.

  17. The stellar mass distribution of S$^{4}$G disk galaxies

    CERN Document Server

    Díaz-García, Simón; Laurikainen, Eija

    2016-01-01

    We use 3.6 $\\mu$m imaging from the S$^{4}$G survey to characterize the typical stellar density profiles ($\\Sigma_{\\ast}$) and bars as a function of fundamental galaxy parameters (e.g. the total stellar mass $M_{\\ast}$), providing observational constraints for galaxy simulation models to be compared with. We rescale galaxy images to a common frame determined by the size in physical units, by their disk scalelength, or by their bar size and orientation. We stack the resized images to obtain statistically representative average stellar disks and bars. For a given $M_{\\ast}$ bin ($\\ge 10^{9}M_{\\odot}$), we find a significant difference in the stellar density profiles of barred and non-barred systems that gives evidence for bar-induced secular evolution of disk galaxies: (i) disks in barred galaxies show larger scalelengths and fainter extrapolated central surface brightnesses, (ii) the mean surface brightness profiles of barred and non-barred galaxies intersect each other slightly beyond the mean bar length, most...

  18. Connecting Galaxy Disk and Extended Halo Gas Kinematics

    CERN Document Server

    Kacprzak, G G; Steidel, C C; Ceverino, D; Klypin, A A; Murphy, M T

    2007-01-01

    We have explored the galaxy disk/extended halo gas kinematic relationship using rotation curves (Keck/ESI) of ten intermediate redshift galaxies which were selected by MgII halo gas absorption observed in quasar spectra. Previous results of six edge-on galaxies, probed along their major axis, suggest that observed halo gas velocities are consistent with extended disk-like halo rotation at galactocentric distances of 25-72 kpc. Using our new sample, we demonstrate that the gas velocities are by and large not consistent with being directly coupled to the galaxy kinematics. Thus, mechanisms other than co-rotation dynamics (i.e., gas inflow, feedback, galaxy-galaxy interactions, etc.) must be invoked to account for the overall observed kinematics of the halo gas. In order to better understand the dynamic interaction of the galaxy/halo/cosmic web environment, we performed similar mock observations of galaxies and gaseous halos in Lambda-CDM cosmological simulations. We discuss an example case of a z=0.92 galaxy wi...

  19. Asymmetric warps in disk galaxies: dependence on dark matter halo

    CERN Document Server

    Jog, K S C J

    2006-01-01

    Recent observations have shown that most of the warps in the disk galaxies are asymmetric. However there exists no generic mechanism to generate these asymmetries in warps. We have shown that a rich variety of possible asymmetries in the z-distribution of the spiral galaxies can naturally arise due to a dynamical wave interference between the first two bending modes i.e. bowl-shaped mode(m=0) and S-shaped warping mode(m=1) in the galactic disk embedded in a dark matter halo. We show that the asymmetric warps are more pronounced when the dark matter content within the optical disk is lower as in early-type galaxies.

  20. The slowing down of galaxy disks in dissipationless minor mergers

    CERN Document Server

    Qu, Yan; Lehnert, Matthew; van Driel, Wim; Jog, Chanda J

    2010-01-01

    We have investigated the impact of dissipationless minor galaxy mergers on the angular momentum of the remnant. Our simulations cover a range of initial orbital characteristics and the system consists of a massive galaxy with a bulge and disk merging with a much less massive (one-tenth or one-twentieth) gasless companion which has a variety of morphologies (disk- or elliptical-like) and central baryonic mass concentrations. During the process of merging, the orbital angular momentum is redistributed into the internal angular momentum of the final system; the internal angular momentum of the primary galaxy can increase or decrease depending on the relative orientation of the orbital spin vectors (direct or retrograde), while the initially non-rotating dark matter halo always gains angular momentum. The specific angular momentum of the stellar component always decreases independent of the orbital parameters or morphology of the satellite, the decrease in the rotation velocity of the primary galaxy is accompanie...

  1. A Photometric Method for Quantifying Asymmetries in Disk Galaxies

    CERN Document Server

    Kornreich, D A; Lovelace, R V E; Kornreich, David A.; Haynes, Martha P.; Lovelace, Richard V.E.

    1998-01-01

    A photometric method for quantifying deviations from axisymmetry in optical images of disk galaxies is applied to a sample of 32 face-on and nearly face-on spirals. The method involves comparing the relative fluxes contained within trapezoidal sectors arranged symmetrically about the galaxy center of light, excluding the bulge and/or barred regions. Such a method has several advantages over others, especially when quantifying asymmetry in flocculent galaxies. Specifically, the averaging of large regions improves the signal-to-noise in the measurements; the method is not strongly affected by the presence of spiral arms; and it identifies the kinds of asymmetry that are likely to be dynamically important. Application of this "method of sectors" to R-band images of 32 disk galaxies indicates that about 30% of spirals show deviations from axisymmetry at the 5-sigma level.

  2. Elliptical Galaxies and Bulges of Disk Galaxies: Summary of Progress and Outstanding Issues

    CERN Document Server

    Kormendy, John

    2015-01-01

    This is the summary chapter of a review book on galaxy bulges. Bulge properties and formation histories are more varied than those of ellipticals. I emphasize two advances: 1 - "Classical bulges" are observationally indistinguishable from ellipticals, and like them, are thought to form by major galaxy mergers. "Disky pseudobulges" are diskier and more actively star-forming (except in S0s) than are ellipticals. Theys are products of the slow ("secular") evolution of galaxy disks: bars and other nonaxisymmetries move disk gas toward the center, where it starbursts and builds relatively flat, rapidly rotating components. This secular evolution is a new area of galaxy evolution work that complements hierarchical clustering. 2 - Disks of high-redshift galaxies are unstable to the formation of mass clumps that sink to the center and merge - an alternative channel for the formation of classical bulges. I review successes and unsolved problems in the formation of bulges+ellipticals and their coevolution (or not) with...

  3. Counter-Rotation in Disk Galaxies

    CERN Document Server

    Corsini, E M

    2014-01-01

    Counter-rotating galaxies host two components rotating in opposite directions with respect to each other. The kinematic and morphological properties of lenticulars and spirals hosting counter-rotating components are reviewed. Statistics of the counter-rotating galaxies and analysis of their stellar populations provide constraints on the formation scenarios which include both environmental and internal processes.

  4. Young star clusters in the outer disks of LITTLE THINGS dwarf irregular galaxies

    CERN Document Server

    Hunter, Deidre A; Gehret, Elizabeth

    2016-01-01

    We examine FUV images of the LITTLE THINGS sample of nearby dwarf irregular (dIrr) and Blue Compact Dwarf (BCD) galaxies to identify distinct young regions in their far outer disks. We use these data, obtained with the Galaxy Evolution Explorer satellite, to determine the furthest radius at which in situ star formation can currently be identified. The FUV knots are found at distances from the center of the galaxies of 1 to 8 disk scale lengths and have ages of <20 Myrs and masses of 20 to 1E5 Msolar. The presence of young clusters and OB associations in the outer disks of dwarf galaxies shows that dIrrs do have star formation taking place there in spite of the extreme nature of the environment. Most regions are found where the HI surface density is ~1 Msolar per pc2, although both the HI and dispersed old stars go out much further. This limiting density suggests a cutoff in the ability to form distinct OB associations and perhaps even stars. We compare the star formation rates in the FUV regions to the ave...

  5. STAR FORMATION IN THE OUTER DISK OF SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Kate L.; Van Zee, Liese [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Cote, Stephanie [Canadian Gemini Office, Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada); Schade, David, E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: Stephanie.Cote@nrc-cnrc.gc.ca, E-mail: David.Schade@nrc-cnrc.gc.ca [Herzberg Institute of Astrophysics, National Research Council of Canada, Victoria (Canada)

    2012-09-20

    We combine new deep and wide field of view H{alpha} imaging of a sample of eight nearby (d Almost-Equal-To 17 Mpc) spiral galaxies with new and archival H I and CO imaging to study the star formation and the star formation regulation in the outer disk. We find that, in agreement with previous studies, star formation in the outer disk has low covering fractions, and star formation is typically organized into spiral arms. The star formation in the outer disk is at extremely low levels, with typical star formation rate surface densities of {approx}10{sup -5} to 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}. We find that the ratio of the radial extent of detected H II regions to the radius of the H I disk is typically {approx}>85%. This implies that in order to further our understanding of the implications of extended star formation, we must further our understanding of the formation of extended H I disks. We measure the gravitational stability of the gas disk, and find that the outer gaseous disk is typically a factor of {approx}2 times more stable than the inner star-forming disk. We measure the surface density of outer disk H I arms, and find that the disk is closer to gravitational instability along these arms. Therefore, it seems that spiral arms are a necessary, but not sufficient, requirement for star formation in the outer disk. We use an estimation of the flaring of the outer gas disk to illustrate the effect of flaring on the Schmidt power-law index; we find that including flaring increases the agreement between the power-law indices of the inner and outer disks.

  6. Internal kinematics of isolated modelled disk galaxies

    CERN Document Server

    Kapferer, W; Schindler, S; Böhm, A; Ziegler, B L

    2005-01-01

    We present a systematic investigation of rotation curves (RCs) of fully hydrodynamically simulated galaxies, including cooling, star formation with associated feedback and galactic winds. Applying two commonly used fitting formulae to characterize the RCs, we investigate systematic effects on the shape of RCs both by observational constraints and internal properties of the galaxies. We mainly focus on effects that occur in measurements of intermediate and high redshift galaxies. We find that RC parameters are affected by the observational setup, like slit misalignment or the spatial resolution and also depend on the evolution of a galaxy. Therefore, a direct comparison of quantities derived from measured RCs with predictions of semi-analytic models is difficult. The virial velocity V_c, which is usually calculated and used by semi-analytic models can differ significantly from fit parameters like V_max or V_opt inferred from RCs. We find that V_c is usually lower than typical characteristic velocities derived ...

  7. Stochastic 2-D Models of Galaxy Disk Evolution. The Galaxy M33

    CERN Document Server

    Mineikis, Tadas

    2015-01-01

    We have developed a fast numerical 2-D model of galaxy disk evolution (resolved along the galaxy radius and azimuth) by adopting a scheme of parameterized stochastic self-propagating star formation. We explore the parameter space of the model and demonstrate its capability to reproduce 1-D radial profiles of the galaxy M33: gas surface density, surface brightness in the i and GALEX FUV passbands, and metallicity.

  8. The formation of disk galaxies in a LCDM universe

    CERN Document Server

    Agertz, Oscar; Moore, Ben

    2010-01-01

    We study the formation of disk galaxies in a fully cosmological framework using adaptive mesh refinement simulations. We perform an extensive parameter study of the main sub-grid processes that control how gas is converted into stars and the coupled effect of supernovae feedback. We argue that previous attempts to form disk galaxies have been unsuccessful because of the universal adoption of strong feedback combined with high star formation efficiencies. Unless extreme amounts of energy are injected into the interstellar medium during supernovae events, these star formation parameters result in bulge dominated S0/Sa galaxies as star formation is too efficient at z~3. We show that a low efficiency of star-formation more closely models the sub-parsec physical processes, especially at high redshift. We highlight the successful formation of extended disk galaxies with scale lengths r_d=4-5 kpc, flat rotation curves and bulge to disk ratios of B/D~1/4. Not only do we resolve the formation of a Milky Way-like spira...

  9. Star formation in the outskirts of disk galaxies

    NARCIS (Netherlands)

    Ferguson, AMN

    2002-01-01

    The far outer regions of galactic disks allow an important probe of both star formation and galaxy formation. I discuss how observations of HII regions in these low gas density, low metallicity environments can shed light on the physical processes which drive galactic star formation. The history of

  10. Angular Momentum in the Formation of Disk Galaxies

    Institute of Scientific and Technical Information of China (English)

    LUO Zhi-Jian; SHU Cheng-Gang

    2004-01-01

    @@ Within the current framework of disk galaxy formation, we discuss the resulted surface-density profiles according to the theoretical angular momentum distributions (AMDs) presented by Bullock et al. [Astrophys. J.555 (2001) 240(B01)] for the ACDM cosmology in both spherical and cylindric coordinates. It is found that the derived surface density distribution of a disk in the outer region is in general similar to an exponential disk for both the theoretical AMDs. In the central region, the results from both the theoretical AMDs are inconsistent with observations whatever the disk bar-instability is taken into account or not. The cylindric form of the theoretical AMD leads to the bar-instability more easily for a give galaxy than that for spherical AMD, which could result in a more massive bulge. After comparing the model predictions with our Milky Way galaxy, we find that the theoretical AMDs predict larger mass fractions of baryons with low angular momentum than the observed ones, which would lead to the disk sizes to be smaller. Two possible processes which could solve the angular momentum problem are discussed.

  11. A scaling law of radial gas distribution in disk galaxies

    Science.gov (United States)

    Wang, Zhong

    1990-01-01

    Based on the idea that local conditions within a galactic disk largely determine the region's evolution time scale, researchers built a theoretical model to take into account molecular cloud and star formations in the disk evolution process. Despite some variations that may be caused by spiral arms and central bulge masses, they found that many late-type galaxies show consistency with the model in their radial atomic and molecular gas profiles. In particular, researchers propose that a scaling law be used to generalize the gas distribution characteristics. This scaling law may be useful in helping to understand the observed gas contents in many galaxies. Their model assumes an exponential mass distribution with disk radius. Most of the mass are in atomic gas state at the beginning of the evolution. Molecular clouds form through a modified Schmidt Law which takes into account gravitational instabilities in a possible three-phase structure of diffuse interstellar medium (McKee and Ostriker, 1977; Balbus and Cowie, 1985); whereas star formation proceeds presumably unaffected by the environmental conditions outside of molecular clouds (Young, 1987). In such a model both atomic and molecular gas profiles in a typical galactic disk (as a result of the evolution) can be fitted simultaneously by adjusting the efficiency constants. Galaxies of different sizes and masses, on the other hand, can be compared with the model by simply scaling their characteristic length scales and shifting their radial ranges to match the assumed disk total mass profile sigma tot(r).

  12. On the Formation of Warped Gas Disks in Galaxies

    CERN Document Server

    Haan, Sebastian

    2014-01-01

    We consider the most commonly occurring circumstances which apply to galaxies, namely membership in galaxy groups of about $10^{13}h^{-1} M_\\odot$ total mass, and estimate the accompanying physical conditions of intergalactic medium (IGM) density and the relative galaxy-IGM space velocity. We then investigate the dynamical consequences of such a typical galaxy-IGM interaction on a rotating gaseous disk within the galaxy potential. We find that the rotating outer disk is systematically distorted into a characteristic "warp" morphology, of the type that has been well-documented in the majority of well-studied nearby systems. The distortion is established rapidly, within two rotation periods, and is long-lived, surviving for at least ten. A second consequence of the interaction is the formation of a one arm retrograde spiral wave pattern that propagates in the disk. We suggest that the ubiquity of the warp phenomenon might be used to reconstruct both the IGM density profile and individual member orbits within ga...

  13. Self-Perpetuating Spiral Arms in Disk Galaxies

    CERN Document Server

    D'Onghia, Elena; Hernquist, Lars

    2012-01-01

    The precise nature of spiral structure in galaxies remains uncertain. Recent studies suggest that spiral arms result from interactions between disks and satellite galaxies. Instead, leaving aside the grand bisymmetric spirals, here we consider the possibility that the multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can survive at least in a statistical sense long after the original perturbing influence has been removed. Our findings thus motivate a ...

  14. HI Imaging Observations of Superthin Galaxies. II. IC2233 and the Blue Compact Dwarf NGC2537

    CERN Document Server

    Matthews, Lynn D

    2007-01-01

    We have used the VLA to image the HI 21-cm line emission in the edge-on Sd galaxy IC2233 and the blue compact dwarf NGC2537. We also present new optical B,R, and H alpha imaging of IC2233 obtained with the WIYN telescope. Despite evidence of localized massive star formation, IC2233 has a low surface brightness disk with a low global star formation rate (~0.05 M_sun/yr), and no significant 21-cm radio continuum emission. The HI and ionized gas disks of IC2233 are clumpy and vertically distended, with scale heights comparable to the young stars. Both the stellar and HI disks of IC2233 appear flared, and we also find a vertically extended, rotationally anomalous HI component extending to z~2.4 kpc. The HI disk exhibits a mild lopsidedness as well as a global corrugation pattern with a period of ~7 kpc and an amplitude of ~150 pc. To our knowledge, this is the first time corrugations of the gas disk have been reported in an external galaxy; these undulations may be linked to bending instabilities or to underlying...

  15. The opacity of spiral galaxy disks. IV. Radial extinction profiles from counts of distant galaxies seen through foreground disks

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. and Holwerda et al. developed the Synthetic Field Method (SFM), which analyzes synthetic

  16. Spatial Orientation of Spin Vectors of Blue-shifted Galaxies

    CERN Document Server

    Yadav, S N; Saurer, W

    2016-01-01

    We present the analysis of the spin vector orientation of 5$\\,$987 SDSS galaxies having negative redshift from $-$87.6 to $-$0.3 km$\\,$s$^{-1}$. Two dimensional observed parameters are used to compute three dimensional galaxy rotation axes by applying `position angle--inclination' method. We aim to examine the non-random effects in the spatial orientation of blue-shifted galaxies. We generate 5$\\times$10$^6$ virtual galaxies to find expected isotropic distributions by performing numerical simulations. We have written MATLAB program to facilitate the simulation process and eliminate the manual errors in the process. Chi-square, auto-correlation, and the Fourier tests are used to examine non-random effects in the polar and azimuthal angle distributions of the galaxy rotation axes. In general, blue-shifted galaxies show no preferred alignments of galaxy rotation axes. Our results support Hierarchy model, which suggests a random orientation of angular momentum vectors of galaxies. However, local effects are noted...

  17. Shrinking Galaxy Disks with Fountain-Driven Accretion from the Halo

    CERN Document Server

    Elmegreen, Bruce G; Hunter, Deidre A

    2014-01-01

    Star formation in most galaxies requires cosmic gas accretion because the gas consumption time is short compared to the Hubble time. This accretion presumably comes from a combination of infalling satellite debris, cold flows, and condensation of hot halo gas at the cool disk interface, perhaps aided by a galactic fountain. In general, the accretion will have a different specific angular momentum than the part of the disk that receives it, even if the gas comes from the nearby halo. Then the gas disk expands or shrinks over time. Here we show that condensation of halo gas at a rate proportional to the star formation rate in the fountain model will preserve an initial shape, such as an exponential, with a shrinking scale length, leaving behind a stellar disk with a slightly steeper profile of younger stars near the center. This process is slow for most galaxies, producing imperceptible radial speeds, and it may be dominated by other torques, but it could be important for Blue Compact Dwarfs, which tend to have...

  18. The universal rotation curve of dwarf disk galaxies

    CERN Document Server

    Karukes, Ekaterina V

    2016-01-01

    We use the concept of the spiral rotation curves universality (see Parsic et al. 1996) to investigate the luminous and dark matter properties of the dwarf disk galaxies in the local volume (size $\\sim11$ Mpc). Our sample includes 36 objects with rotation curves carefully selected from the literature. We find that, despite the large variations of our sample in luminosities ($\\sim$ 2 of dex), the rotation curves in specifically normalized units, look all alike and lead to the lower-mass version of the universal rotation curve of spiral galaxies found in Parsic et al. 1996. We mass model $V(R/R_{opt})/V_{opt}$, the double normalized universal rotation curve of dwarf disk galaxies: the results show that these systems are totally dominated by dark matter whose density shows a core size between 2 and 3 stellar disk scale lengths. Similar to galaxies of different Hubble types and luminosities, the core radius $r_0$ and the central density $\\rho_0$ of the dark matter halo of these objects are related by $ \\rho_0 r_0 ...

  19. Low Angular Momentum in Clumpy, Turbulent Disk Galaxies

    Science.gov (United States)

    Obreschkow, Danail; Glazebrook, Karl; Bassett, Robert; Fisher, David B.; Abraham, Roberto G.; Wisnioski, Emily; Green, Andrew W.; McGregor, Peter J.; Damjanov, Ivana; Popping, Attila; Jørgensen, Inger

    2015-12-01

    We measure the stellar specific angular momentum {j}s={J}s/{M}s in four nearby (z ≈ 0.1) disk galaxies that have stellar masses {M}s near the break {M}s* of the galaxy mass function but look like typical star-forming disks at z ≈ 2 in terms of their low stability (Q ≈ 1), clumpiness, high ionized gas dispersion (40-50 {km} {{{s}}}-1), high molecular gas fraction (20%-30%), and rapid star formation (˜ 20{M}⊙ {{yr}}-1). Combining high-resolution (Keck-OSIRIS) and large-radius (Gemini-GMOS) spectroscopic maps, only available at low z, we discover that these targets have ˜ 3 times less stellar angular momentum than typical local spiral galaxies of equal stellar mass and bulge fraction. Theoretical considerations show that this deficiency in angular momentum is the main cause of their low stability, while the high gas fraction plays a complementary role. Interestingly, the low {j}s values of our targets are similar to those expected in the {M}s* population at higher z from the approximate theoretical scaling {j}s\\propto {(1+z)}-1/2 at fixed {M}s. This suggests that a change in angular momentum, driven by cosmic expansion, is the main cause for the remarkable difference between clumpy {M}s* disks at high z (which likely evolve into early-type galaxies) and mass-matched local spirals.

  20. Stellar nuclei and inner polar disks in lenticular galaxies

    CERN Document Server

    Sil'chenko, Olga K

    2016-01-01

    I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of Isaac Newton Group. I estimate also the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with running tilted-ring technique, I have found 7 new cases of the inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10% that is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample implying similar histories of multiple gas accretion events from various directions.

  1. Stellar Nuclei and Inner Polar Disks in Lenticular Galaxies

    Science.gov (United States)

    Sil'chenko, Olga K.

    2016-09-01

    I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.

  2. The Parker Instability in Disk Galaxies

    CERN Document Server

    Rodrigues, Luiz Felippe S; Shukurov, Anvar; Bushby, Paul J; Fletcher, Andrew

    2016-01-01

    We examine the evolution of the Parker instability in galactic disks using 3D numerical simulations. We consider a local Cartesian box section of a galactic disk, where gas, magnetic fields and cosmic rays are all initially in a magnetohydrostatic equilibrium. This is done for different choices of initial cosmic ray density and magnetic field. The growth rates and characteristic scales obtained from the models, as well as their dependences on the density of cosmic rays and magnetic fields, are in broad agreement with previous (linearized, ideal) analytical work. However, this non-ideal instability develops a multi-modal 3D structure, which cannot be quantitatively predicted from the earlier linearized studies. This 3D signature of the instability will be of importance in interpreting observations. As a preliminary step towards such interpretations, we calculate synthetic polarized intensity and Faraday rotation measure maps, and the associated structure functions of the latter, from our simulations; these sug...

  3. Disk heating and bending instability in galaxies with counterrotation

    CERN Document Server

    Khoperskov, Sergey

    2016-01-01

    With the help of high-resolution long-slit and integral-field spectroscopy observations, the number of confirmed cases of galaxies with counterrotation is increasing rapidly. The evolution of such counterrotating galaxies remains far from being well understood. In this paper we study the dynamics of counterrotating collisionless stellar disks by means of $N$-body simulations. We show that, in the presence of counterrotation, an otherwise gravitationally stable disk can naturally generate bending waves accompanied by strong disk heating across the disk plane, that is in the vertical direction. Such conclusion is found to hold even for dynamically warm systems with typical values of the initial vertical-to-radial velocity dispersion ratio $\\sigma_{\\rm R}/\\sigma_{\\rm z} \\approx 0.5$, for which the role of pressure anisotropy should be unimportant. We note that, during evolution, the $\\sigma_{\\rm R}/\\sigma_{\\rm z}$ ratio tends to rise up to values close to unity in the case of locally Jeans-stable disks, whereas ...

  4. Disk galaxies with broken luminosity profiles from cosmological simulations

    CERN Document Server

    Martínez-Serrano, Francisco J; Doménech-Moral, Mariola; Domínguez-Tenreiro, Rosa

    2009-01-01

    We simulate the cosmological formation of three disk galaxies using the zoom-in technique and including a detailed treatment of chemical evolution and cooling. The resulting galaxies have a rather high disk-to-total ratio for a cosmological simulation and thin stellar disks. They present a break in the luminosity profile at 3.0 +- 0.5 disk scale lengths, while showing an exponential mass profile without any apparent breaks, in line with recent observational results. Since the stellar mass profile is exponential, only differences in the stellar populations can be the cause of the luminosity break. Although we find a cutoff for the star formation rate imposed by a density threshold in our star formation model, it does not coincide with the luminosity break and is located at 4.3 +- 0.4 disk scale lengths, with star formation going on between both radii. The color profiles and the age profiles are "U-shaped", with the minimum for both profiles located approximately at the break radius. The SFR to stellar mass rat...

  5. UGC8802: A Massive Disk Galaxy in Formation

    CERN Document Server

    Moran, Sean M; Heckman, Timothy M; Gracia-Carpio, Javier; Saintonge, Amelie; Catinella, Barbara; Wang, Jing; Chen, Yan-Mei; Tacconi, Linda; Schminovich, David; Cox, Pierre; Giovanelli, Riccardo; Haynes, Martha; Kramer, Carsten

    2010-01-01

    We report new observations of the galaxy UGC8802 obtained through GASS, the GALEX Arecibo SDSS Survey, which show this galaxy to be in a remarkable evolutionary state. UGC8802 (GASS35981) is a disk galaxy with stellar mass M*=2x10^10 Msolar which appears to contain an additional 2.1x10^10 Msolar of HI gas. New millimeter observations with the IRAM 30m telescope indicate a molecular gas mass only a tenth this large. Using deep long-slit spectroscopy, we examine the spatially resolved star formation rate and metallicity profiles of GASS35981 for clues to its history. We find that the star formation surface density in this galaxy is low (Sigma_SFR=0.003 Msolar/yr/kpc^2) and that the star formation is spread remarkably evenly across the galaxy. The low molecular gas masses measured in our three IRAM pointings are largely consistent with the total star formation measured within the same apertures. Our MMT long-slit spectrum reveals a sharp drop in metallicity in the outer disk of GASS35981. The ratio of current st...

  6. Virial-to-optical velocity ratios of local disk galaxies from combined kinematics and galaxy-galaxy lensing

    CERN Document Server

    Reyes, Reinabelle; Gunn, James E; Nakajima, Reiko; Seljak, Uros; Hirata, Chris M

    2011-01-01

    In this paper, we measure the virial-to-optical velocity ratios V_vir/V_opt of disk galaxies in the Sloan Digital Sky Survey (SDSS) at a mean redshift of = 0.07 and with stellar masses 10^9 M_sun < M_* < 10^11 M_sun. V_vir/V_opt, the ratio of the circular velocity measured at the virial radius of the dark matter halo (~150 kpc) to that at the optical radius of the disk (~10 kpc), is a powerful observational constraint on disk galaxy formation. It links galaxies to their dark matter haloes dynamically and constrains the total mass profile of disk galaxies over an order of magnitude in length scale. For this measurement, we combine V_vir derived from halo masses measured with galaxy-galaxy lensing, with V_opt derived from the Tully-Fisher relation (TFR) from Reyes et al. (2011). In anticipation of this combination, we use similarly-selected galaxy samples for both the lensing and TFR analysis. For three M_* bins with lensing-weighted mean stellar masses of 0.6, 2.7, and 6.5 x 10^10 M_sun, we find halo-to...

  7. Dynamical Stability and Galaxy Evolution in LSB Disk Galaxies

    NARCIS (Netherlands)

    Mihos, C.; McGaugh, S. S.; Blok, E. de

    1996-01-01

    Published in: AIP Conf. Proc. 393 (1997) , pp.311 citations recorded in [Science Citation Index] Abstract: We demonstrate that, due to their low surface mass density and large dark matter content, LSB disks are quite stable against the growth of global bar modes. However, they may be only marginally

  8. Properties of Disk Galaxies in a Hierarchical Formation Scenario

    Science.gov (United States)

    Avila-Reese, Vladimir; Firmani, Claudio

    2000-04-01

    We used galaxy evolutionary models in a hierarchical inside-out disk formation scenario to study the origin of the main local and global properties of disk galaxies as well as their correlations. We found that most of these properties and correlations are the result of three (cosmological) initial factors and their dispersions: the virial mass, the halo mass aggregation history (MAH), and the angular momentum given through the spin parameter lambda. The MAH determines mainly the halo structure and the integral color indexes while Lambda determines mainly the surface brightness and the bulge-to-disk ratio. We calculated star formation (SF) using a gravitational instability criterion and a self-regulation mechanism in the disk turbulent ISM. The efficiency of SF in this model is almost independent from the mass. We show that the luminosity- dependent dust absorption empirically determined by Wang & Heckman explains the observed color-magnitude and color Tully-Fisher (TF) relations without the necessity of introducing a mass-dependent SF efficiency. The disks in centrifugal equilibrium form within growing cold dark matter halos with a gas accretion rate proportional to the rate of the MAH. The disks present exponential surface density and brightness profiles, negative radial color index gradients, and nearly flat rotation curves. We also calculated the secular formation of a bulge due to gravitational instabilities in the stellar disk. The intensive properties of our models agree with the observational data and the trends of the Hubble sequence are reproduced. The predicted infrared TF and luminosity-radius relations also agree with observations. The main shortcomings of our inside-out hierarchical models are the excessive radial color gradients and the dark halo dominion in the rotation curve decompositions.

  9. Neutron Star Motion in the Disk Galaxy

    Institute of Scientific and Technical Information of China (English)

    WEI Ying-Chun; A.Taani; PAN Yuan-Yue; WANG Jing; CAI Yan; LIU Gao-Chao; LUO A-Li; ZHANG Hong-Bo; ZHAO Yong-Heng

    2010-01-01

    @@ The neutron star motions are based on the undisturbed finitely thick galactic disk gravitational potential model.Two initial conditions,I.e.the locations and velocities,are considered.The Monte Carlo method is employed to separate rich diversities of the orbits of neutron stars into several sorts.The Poincaré section has the potential to play an important role in the diagnosis of the neutron star motion.It has been observed that the increasing ratio of the motion range vertical to the galactic plane to that parallel to the galactic plane results in the irregularity of neutron star motion.

  10. Properties of disk galaxies in a hierarchical formation scenario

    CERN Document Server

    Avila-Reese, V

    2000-01-01

    We used galaxy evolutionary models in a hierarchical inside-out formation scenario to study the origin of the main properties and correlations of disk galaxies. We found that most of these properties and correlations are the result of three (cosmological) initial factors and their dispersions: the virial mass, the halo mass aggregation history (MAH), and the angular momentum given through the spin parameter \\lambda. The MAH determines mainly the halo structure and the color indexes while \\lambda determines mainly the surface brightness and the bulge-to-disk ratio. We calculated star formation (SF) using a gravitational instability criterion and a self-regulation mechanism in the turbulent ISM. The efficiency of SF in this model is almost independent from the mass. We show that the luminosity-dependent dust absorption empirically determined by Wang & Heckman explains the observed color-magnitude and color Tully-Fisher (TF) relations without the necessity of introducing a mass-dependent SF efficiency. The d...

  11. A new spin on disks of satellite galaxies

    CERN Document Server

    Cautun, Marius; Frenk, Carlos S; Sawala, Till

    2014-01-01

    We investigate the angular and kinematic distributions of satellite galaxies around a large sample of bright isolated primaries in the spectroscopic and photometric catalogues of the Sloan Digital Sky Survey (SDSS). We detect significant anisotropy in the spatial distribution of satellites. To test whether this anisotropy could be related to the rotating disks of satellites recently found by Ibata et al. in a sample of SDSS galaxies, we repeat and extend their analysis. Ibata et al. found an excess of satellites on opposite sides of their primaries having anticorrelated radial velocities. We find that this excess is sensitive to small changes in the sample selection criteria which can greatly reduce its significance. In addition, we find no evidence for correspondingly correlated velocities for satellites observed on the same side of their primaries, which would be expected for rotating disks of satellites. We conclude that the detection of coherent rotation in the satellite population in current observationa...

  12. Prominent spiral arms in the gaseous outer galaxy disks

    CERN Document Server

    Bertin, G

    2009-01-01

    Context: Several spiral galaxies, as beautifully exhibited by the case of NGC 6946, display a prominent large-scale spiral structure in their gaseous outer disk. Such structure is often thought to pose a dynamical puzzle, because grand-design spiral structure is traditionally interpreted as the result of density waves carried mostly in the stellar disk. Aims. Here we argue that the outer spiral arms in the cold gas outside the bright optical disk actually have a natural interpretation as the manifestation of the mechanism that excites grand-design spiral structure in the main, star-dominated body of the disk: the excitation is driven by angular momentum transport to the outer regions, through trailing density waves outside the corotation circle that can penetrate beyond the Outer Lindblad Resonance in the gaseous component of the disk. Methods: Because of conservation of the density wave action, these outgoing waves are likely to become more prominent in the outer disk and eventually reach non-linear amplitud...

  13. Dynamics of barred galaxies: effects of disk height

    CERN Document Server

    Klypin, A; Colin, P; Quinn, T

    2008-01-01

    We study dynamics of bars in models of disk galaxies embeded in realistic dark matter halos. We find that disk thickness plays an important, if not dominant, role in the evolution and structure of the bars. We also make extensive numerical tests of different N-body codes used to study bar dynamics. Models with thick disks typically used in this type of modeling (height-to-length ratio hz/Rd=0.2) produce slowly rotating, and very long, bars. In contrast, more realistic thin disks with the same parameters as in our Galaxy (hz/Rd= 0.1) produce bars with normal length Rbar approx R_d, which rotate quickly with the ratio of the corotation radius to the bar radius 1.2-1.4 compatible with observations. Bars in these models do not show a tendency to slow down, and may lose as little as 2-3 percent of their angular momentum due to dynamical friction with the dark matter over cosmological time. We attribute the differences between the models to a combined effect of high phase-space density and smaller Jeans mass in the...

  14. Ejection of Supernova-Enriched Gas From Dwarf Disk Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Fragile, P C; Murray, S D; Lin, D C

    2004-06-15

    We examine the efficiency with which supernova-enriched gas may be ejected from dwarf disk galaxies, using a methodology previously employed to study the self-enrichment efficiency of dwarf spheroidal systems. Unlike previous studies that focused on highly concentrated starbursts, in the current work we consider discrete supernova events spread throughout various fractions of the disk. We model disk systems having gas masses of 10{sup 8} and 10{sup 9} M{sub {circle_dot}} with supernova rates of 30, 300, and 3000 Myr{sup -1}. The supernova events are confined to the midplane of the disk, but distributed over radii of 0, 30, and 80% of the disk radius, consistent with expectations for Type II supernovae. In agreement with earlier studies, we find that the enriched material from supernovae is largely lost when the supernovae are concentrated near the nucleus, as expected for a starburst event. In contrast, we find the loss of enriched material to be much less efficient (as low as 21%) when the supernovae occur over even a relatively small fraction of the disk. The difference is due to the ability of the system to relax following supernova events that occur over more extended regions. Larger physical separations also reduce the likelihood of supernovae going off within low-density ''chimneys'' swept out by previous supernovae. We also find that, for the most distributed systems, significant metal loss is more likely to be accompanied by significant mass loss. A comparison with theoretical predications indicates that, when undergoing self-regulated star formation, galaxies in the mass range considered shall efficiently retain the products of Type II supernovae.

  15. Effects of Supernova Feedback on the Formation of Galaxy Disks

    CERN Document Server

    Scannapieco, Cecilia; White, Simon D M; Springel, Volker

    2008-01-01

    We use cosmological simulations in order to study the effects of supernova (SN) feedback on the formation of a Milky Way-type galaxy of virial mass ~10^12 M_sun/h. We analyse a set of simulations run with the code described by Scannapieco et al. (2005, 2006), where we have tested our star formation and feedback prescription using isolated galaxy models. Here we extend this work by simulating the formation of a galaxy in its proper cosmological framework, focusing on the ability of the model to form a disk-like structure in rotational support. We find that SN feedback plays a fundamental role in the evolution of the simulated galaxy, efficiently regulating the star formation activity, pressurizing the gas and generating mass-loaded galactic winds. These processes affect several galactic properties such as final stellar mass, morphology, angular momentum, chemical properties, and final gas and baryon fractions. In particular, we find that our model is able to reproduce extended disk components with high specifi...

  16. Misaligned Disks as Obscurers in Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, A.; Elvis, M.; /Edinburgh U., Inst. Astron. /Harvard-Smithsonian Ctr. Astrophys.

    2010-06-02

    We review critically the evidence concerning the fraction of Active Galactic Nuclei (AGN) which appear as Type 2 AGN, carefully distinguishing strict Type 2 AGN from both more lightly reddened Type 1 AGN, and from low excitation narrow line AGN, which may represent a different mode of activity. Low excitation AGN occur predominantly at low luminosities; after removing these, true Type 2 AGN represent 58{-+}5% of all AGN, and lightly reddened Type 1 AGN a further {approx}15%. Radio, IR, and volume-limited samples all agree in showing no change of Type 2 fraction with luminosity. X-ray samples do show a change with luminosity; we discuss possible reasons for this discrepancy. We test a very simple picture which produces this Type 2 fraction with minimal assumptions. In this picture, infall from large scales occurs in random directions, but must eventually align with the inner accretion flow, producing a severely warped disk on parsec scales. If the re-alignment is dominated by tilt, with minimal twist, a wide range of covering factors is predicted in individual objects, but with an expected mean fraction of Type 2 AGN of exactly 50%. This 'tilted disc' picture predicts reasonable alignment of observed nuclear structures on average, but with distinct misalignments in individual cases. Initial case studies of the few well resolved objects show that such misalignments are indeed present.

  17. The Relative Orientation of Nuclear Accretion and Galaxy Stellar Disks in Seyfert Galaxies

    CERN Document Server

    Nagar, N M

    1999-01-01

    We use the difference (delta) between the position angles of the nuclear radio emission and the host galaxy major axis to investigate the distribution of the angle (beta) between the axes of the nuclear accretion disk and the host galaxy disk in Seyfert galaxies. We provide a critical appraisal of the quality of all measurements, and find that the data are limited by observational uncertainties and biases, such as the well known deficiency of Seyfert galaxies of high inclination. There is weak evidence that the distribution of delta for Seyfert 2 galaxies may be different (at the 90% confidence level) from a uniform distribution, while the Seyfert 1 delta distribution is not significantly different from a uniform distribution or from the Seyfert 2 delta distribution. The cause of the possible non-uniformity in the distribution of delta for Seyfert 2 galaxies is discussed. Seyfert nuclei in late-type spiral galaxies may favor large values of delta (at the ~96% confidence level), while those in early-type galax...

  18. The BlueTides Simulation: First Galaxies and Reionization

    CERN Document Server

    Feng, Yu; Croft, Rupert A; Bird, Simeon; Battaglia, Nicholas; Wilkins, Stephen

    2015-01-01

    We introduce the BlueTides simulation and report initial results for the luminosity functions of the first galaxies and AGN, and their contribution to reionization. BlueTides was run on the BlueWaters cluster at NCSA from $z=99$ to $z=8.0$ and includes 2$\\times$7040$^3$ particles in a $400$Mpc/h per side box, making it the largest hydrodynamic simulation ever performed at high redshift. BlueTides includes a pressure-entropy formulation of smoothed particle hydrodynamics, gas cooling, star formation (including molecular hydrogen), black hole growth and models for stellar and AGN feedback processes. The star formation rate density in the simulation is a good match to current observational data at $z\\sim 8-10$. We find good agreement between observations and the predicted galaxy luminosity function in the currently observable range $-18\\le M_{\\mathrm UV} \\le -22.5$ with some dust extinction required to match the abundance of brighter objects. BlueTides implements a patchy reionization model that produces a fluct...

  19. Strongly baryon-dominated disk galaxies at the peak of galaxy formation ten billion years ago

    Science.gov (United States)

    Genzel, R.; Schreiber, N. M. Förster; Übler, H.; Lang, P.; Naab, T.; Bender, R.; Tacconi, L. J.; Wisnioski, E.; Wuyts, S.; Alexander, T.; Beifiori, A.; Belli, S.; Brammer, G.; Burkert, A.; Carollo, C. M.; Chan, J.; Davies, R.; Fossati, M.; Galametz, A.; Genel, S.; Gerhard, O.; Lutz, D.; Mendel, J. T.; Momcheva, I.; Nelson, E. J.; Renzini, A.; Saglia, R.; Sternberg, A.; Tacchella, S.; Tadaki, K.; Wilman, D.

    2017-03-01

    In the cold dark matter cosmology, the baryonic components of galaxies—stars and gas—are thought to be mixed with and embedded in non-baryonic and non-relativistic dark matter, which dominates the total mass of the galaxy and its dark-matter halo. In the local (low-redshift) Universe, the mass of dark matter within a galactic disk increases with disk radius, becoming appreciable and then dominant in the outer, baryonic regions of the disks of star-forming galaxies. This results in rotation velocities of the visible matter within the disk that are constant or increasing with disk radius—a hallmark of the dark-matter model. Comparisons between the dynamical mass, inferred from these velocities in rotational equilibrium, and the sum of the stellar and cold-gas mass at the peak epoch of galaxy formation ten billion years ago, inferred from ancillary data, suggest high baryon fractions in the inner, star-forming regions of the disks. Although this implied baryon fraction may be larger than in the local Universe, the systematic uncertainties (owing to the chosen stellar initial-mass function and the calibration of gas masses) render such comparisons inconclusive in terms of the mass of dark matter. Here we report rotation curves (showing rotation velocity as a function of disk radius) for the outer disks of six massive star-forming galaxies, and find that the rotation velocities are not constant, but decrease with radius. We propose that this trend arises because of a combination of two main factors: first, a large fraction of the massive high-redshift galaxy population was strongly baryon-dominated, with dark matter playing a smaller part than in the local Universe; and second, the large velocity dispersion in high-redshift disks introduces a substantial pressure term that leads to a decrease in rotation velocity with increasing radius. The effect of both factors appears to increase with redshift. Qualitatively, the observations suggest that baryons in the early

  20. Environment Dependence of Disk Morphology of Spiral Galaxies

    CERN Document Server

    Ann, H B

    2014-01-01

    We analyze the dependence of disk morphology (arm class, Hubble type, bar type) of nearby spiral galaxies on the galaxy environment by using local background density ($\\Sigma_{n}$), projected distance ($r_{p}$), and tidal index ($TI$) as measures of the environment. There is a strong dependence of arm class and Hubble type on the galaxy environment, while the bar type exhibits a weak dependence with a high frequency of SB galaxies in high density regions. Grand design fractions and early-type fractions increase with increasing $\\Sigma_{n}$, $1/r_{p}$, and $TI$, while fractions of flocculent spirals and late-type spirals decrease. Multiple-arm and intermediate-type spirals exhibit nearly constant fractions with weak trends similar to grand design and early-type spirals. While bar types show only a marginal dependence on $\\Sigma_{n}$, they show a fairly clear dependence on $r_{p}$ with a high frequency of SB galaxies at small $r_{p}$. The arm class also exhibits a stronger correlation with $r_{p}$ than $\\Sigma_...

  1. Gas-Rich Mergers in LCDM: Disk Survivability and the Baryonic Assembly of Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; /UC, Irvine; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC; Maller, Ariyeh H.; /New York City Coll. Tech.

    2009-08-03

    We use N-body simulations and observationally-normalized relations between dark matter halo mass, stellar mass, and cold gas mass to derive robust expectations about the baryonic content of major mergers out to redshift z {approx} 2. First, we find that the majority of major mergers (m/M > 0.3) experienced by Milky Way size dark matter halos should have been gas-rich, and that gas-rich mergers are increasingly common at high redshift. Though the frequency of major mergers into galaxy halos in our simulations greatly exceeds the observed late-type galaxy fraction, the frequency of gas-poor major mergers is consistent with the observed fraction of bulge-dominated galaxies across the halo mass range M{sub DM} {approx} 10{sup 11} - 10{sup 13} M{sub {circle_dot}}. These results lend support to the conjecture that mergers with high baryonic gas fractions play an important role in building and/or preserving disk galaxies in the universe. Secondly, we find that there is a transition mass below which a galaxy's past major mergers were primarily gas-rich and above which they were gas poor. The associated stellar mass scale corresponds closely to that marking the observed bimodal division between blue, star-forming, disk-dominated systems and red, bulge-dominated systems with old populations. Finally, we find that the overall fraction of a galaxy's cold baryons deposited directly via major mergers is substantial. Approximately 30% of the cold baryonic material in M{sub star} {approx} 10{sup 10} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 11.5} M{sub {circle_dot}}) galaxies is accreted as cold gas in major mergers. For more massive galaxies with M{sub star} {approx} 10{sup 11} M{sub {circle_dot}} (M{sub DM} {approx} 10{sup 13} M{sub {circle_dot}} the fraction of baryons amassed in mergers is even higher, {approx} 50%, but most of these accreted baryons are delivered directly in the form of stars. This baryonic mass deposition is almost unavoidable, and provides a

  2. Merger Histories of Galaxy Halos and Implications for Disk Survival

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, Kyle R.; Bullock, James S.; Wechsler, Risa H.; Maller, Ariyeh H.; Zentner, Andrew R.

    2008-05-16

    The authors study the merger histories of galaxy dark matter halos using a high resolution {Lambda}CDM N-body simulation. The merger trees follow {approx} 17,000 halos with masses M{sub 0} = (10{sup 11} - 10{sup 13})h{sup -1}M{sub {circle_dot}} at z = 0 and track accretion events involving objects as small as m {approx_equal} 10{sup 10} h{sup -1}M{sub {circle_dot}}. They find that mass assembly is remarkably self-similar in m/M{sub 0}, and dominated by mergers that are {approx}10% of the final halo mass. While very large mergers, m {approx}> 0.4 M{sub 0}, are quite rare, sizeable accretion events, m {approx} 0.1 M{sub 0}, are common. Over the last {approx} 10 Gyr, an overwhelming majority ({approx} 95%) of Milky Way-sized halos with M{sub 0} = 10{sup 12} h{sup -1}M{sub {circle_dot}} have accreted at least one object with greater total mass than the Milky Way disk (m > 5 x 10{sup 10} h{sup -1}M{sub {circle_dot}}), and approximately 70% have accreted an object with more than twice that mass (m > 10{sup 11} h{sup -1}M{sub {circle_dot}}). The results raise serious concerns about the survival of thin-disk dominated galaxies within the current paradigm for galaxy formation in a {Lambda}CDM universe. in order to achieve a {approx} 70% disk-dominated fraction in Milky Way-sized {Lambda}CDM halos, mergers involving m {approx_equal} 2 x 10{sup 11} h{sup -1}M{sub {circle_dot}} objects must not destroy disks. Considering that most thick disks and bulges contain old stellar populations, the situation is even more restrictive: these mergers must not heat disks or drive gas into their centers to create young bulges.

  3. Low Angular Momentum in Clumpy, Turbulent Disk Galaxies

    CERN Document Server

    Obreschkow, Danail; Bassett, Robert; Fisher, David B; Abraham, Roberto G; Wisnioski, Emily; Green, Andrew W; McGregor, Peter J; Damjanov, Ivana; Popping, Attila; Jorgensen, Inger

    2015-01-01

    We measure the stellar specific angular momentum jstar=Jstar/Mstar in four nearby (redshift z~0.1) disk galaxies that have stellar masses Mstar near the break M* of the galaxy mass function, but look like typical star-forming disks at z~2 in terms of their low stability (Q~1), clumpiness, high ionized gas dispersion (40-50 km/s), high molecular gas fraction (20-30%) and rapid star formation (~20 Msun/yr). Combining high-resolution (Keck-OSIRIS) and large-radius (Gemini-GMOS) spectroscopic maps, only available at low z, we discover that these targets have ~3 times less stellar angular momentum than typical local spiral galaxies of equal stellar mass and bulge fraction. Theoretical considerations show that this deficiency in angular momentum is the main cause of their low stability, while the high gas fraction plays a complementary role. Interestingly, the low jstar values of our targets are similar to those expected in the M*-population at higher z from the approximate theoretical scaling jstar~(1+z)^(-1/2) at...

  4. Search for Blue Compact Dwarf Galaxies During Quiescence

    CERN Document Server

    Almeida, J Sanchez; Amorin, R; Aguerri, J A; Sanchez-Janssen, R; Tenorio-Tagle, G

    2008-01-01

    Blue Compact Dwarf (BCD) galaxies are metal poor systems going through a major starburst that cannot last for long. We have identified galaxies which may be BCDs during quiescence (QBCD), i.e., before the characteristic starburst sets in or when it has faded away. These QBCD galaxies are assumed to be like the BCD host galaxies. The SDSS/DR6 database provides ~21500 QBCD candidates. We also select from SDSS/DR6 a complete sample of BCD galaxies to serve as reference. The properties of these two galaxy sets have been computed and compared. The QBCD candidates are thirty times more abundant than the BCDs, with their luminosity functions being very similar except for the scaling factor, and the expected luminosity dimming associated with the end of the starburst. QBCDs are redder than BCDs, and they have larger HII region based oxygen abundance. QBCDs also have lower surface brightness. The BCD candidates turn out to be the QBCD candidates with the largest specific star formation rate (actually, with the largest...

  5. Self-perpetuating Spiral Arms in Disk Galaxies

    Science.gov (United States)

    D'Onghia, Elena; Vogelsberger, Mark; Hernquist, Lars

    2013-03-01

    The causes of spiral structure in galaxies remain uncertain. Leaving aside the grand bisymmetric spirals with their own well-known complications, here we consider the possibility that multi-armed spiral features originate from density inhomogeneities orbiting within disks. Using high-resolution N-body simulations, we follow the motions of stars under the influence of gravity, and show that mass concentrations with properties similar to those of giant molecular clouds can induce the development of spiral arms through a process termed swing amplification. However, unlike in earlier work, we demonstrate that the eventual response of the disk can be highly non-linear, significantly modifying the formation and longevity of the resulting patterns. Contrary to expectations, ragged spiral structures can thus survive at least in a statistical sense long after the original perturbing influence has been removed.

  6. Constraints on Accretion Disk Physics in Low Luminosity Radio Galaxies

    Science.gov (United States)

    Baum, Stefi; Noel-Storr, Jacob; O'Dea, Christopher

    2008-03-01

    It is currently believed that essentially all galaxies harbor a massive black hole in their nuclei. If this is true, then it becomes hard to understand why we do not see the luminosity released by the inevitable accretion of the galaxy ISM onto the black hole in all galaxies. The differences in AGN output between the two classes of narrow-line radio galaxies (FRI and FRII) may hold the vital clue. High radio luminosity FRIIs generally show strong high-excitation narrow lines and are believed to be the obscured counterparts of radio loud quasars. Low radio luminosity FRIs by contrast have weaker, low-ionization lines and low ratios of optical to radio luminosities. A large difference in accretion rate and radiative efficiency between FRI and FRIIs would explain the difference in the optical properties and also provide a new unification between different classes of active galaxies in which the dominant parameter is accretion rate. Spitzer IRAC and MIPS observations already exist for most of a well defined sample of FRIs. However, the previously observed objects are the 'famous' ones, e.g., M87, M84, NGC315, 3C264, 3C31. Thus, the existing datasets are highly selected. Here we propose a very small request to complete the sample. We propose IRAC observations in all 4 bands, and MIPS photometry at 24 and 70 microns of 8, and 7 sources, respectively, for a total request of 1.7 hrs. These observations will complete the sample at very little cost in observing time. The large amount of existing complmentary data at multiple wavebands will greatly enhance the legacy value of the proposed observations. By completing the sample, the proposed IRAC and MIPS observations will produce a well defined and very well studied sample of nearby low luminosity radio galaxies. We will use the completed sample to investigate the properties of the accretion disk radiation, and the circumnuclear obscuring material.

  7. Extragalactic SETI: The Tully-Fisher relation as probe of Dysonian astroengineering in disk galaxies

    CERN Document Server

    Zackrisson, E; Asadi, S; Nyholm, A

    2015-01-01

    If advanced extraterrestrial civilizations choose to construct vast numbers of Dyson spheres to harvest radiation energy, this could affect the characteristics of their host galaxies. Potential signatures of such astroengineering projects include reduced optical luminosity, boosted infrared luminosity and morphological anomalies. Here, we apply a technique pioneered by Annis (1999) to search for Kardashev type III civilizations in disk galaxies, based on the predicted offset of these galaxies from the optical Tully-Fisher relation. By analyzing a sample of 1359 disk galaxies, we are able to set a conservative upper limit at 3% on the fraction of local disks subject to Dysonian astroengineering on galaxy-wide scales. However, the available data suggests that a small subset of disk galaxies actually may be underluminous with respect to the Tully-Fisher relation in the way expected for Kardashev type III objects. Based on the optical morphologies and infrared-to-optical luminosity ratios of such galaxies in our ...

  8. Simulations of disk galaxies with cosmic ray driven galactic winds

    CERN Document Server

    Booth, C M; Kravtsov, Andrey V; Gnedin, Nickolay Y

    2013-01-01

    We present results from high-resolution hydrodynamic simulations of isolated SMC- and Milky Way-sized galaxies that include a model for feedback from galactic cosmic rays (CRs). We find that CRs are naturally able to drive winds with mass loading factors of up to ~10 in dwarf systems. The scaling of the mass loading factor with circular velocity between the two simulated systems is consistent with \\propto v_c^{1-2} required to reproduce the faint end of the galaxy luminosity function. In addition, simulations with CR feedback reproduce both the normalization and the slope of the observed trend of wind velocity with galaxy circular velocity. We find that winds in simulations with CR feedback exhibit qualitatively different properties compared to SN driven winds, where most of the acceleration happens violently in situ near star forming sites. In contrast, the CR-driven winds are accelerated gently by the large-scale pressure gradient established by CRs diffusing from the star-forming galaxy disk out into the h...

  9. Revealing the nature of star forming blue early-type galaxies at low redshift

    CERN Document Server

    George, Koshy

    2015-01-01

    Context: Star forming early-type galaxies with blue optical colours at low redshift can be used to test our current understanding of galaxy formation and evolution. Aims: We want to reveal the fuel and triggering mechanism for star formation in these otherwise passively evolving red and dead stellar systems. Methods: We undertook an optical and ultraviolet study of 55 star forming blue early-type galaxies, searching for signatures of recent interactions that could be driving the molecular gas into the galaxy and potentially triggering the star formation. Results: We report here our results on star forming blue early-type galaxies with tidal trails and in close proximity to neighbouring galaxies that are evidence of ongoing or recent interactions between galaxies. There are 12 galaxies with close companions with similar redshifts, among which two galaxies are having ongoing interactions that potentially trigger the star formation. Two galaxies show a jet feature that could be due to the complete tidal disrupti...

  10. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    CERN Document Server

    Assef, R J; Brightman, M; Stern, D; Alexander, D; Bauer, F; Blain, A W; Diaz-Santos, T; Eisenhardt, P R M; Finkelstein, S L; Hickox, R C; Tsai, C -W; Wu, J W

    2015-01-01

    Hot Dust-Obscured Galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the WISE mission from their very red mid-IR colors, and characterized by hot dust temperatures ($T>60~\\rm K$). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured AGN that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of 8 Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot D...

  11. The shape of galaxy disks : How the scale height increases with galactocentric distance

    NARCIS (Netherlands)

    Grijs, R. de; Peletier, R. F.

    1997-01-01

    We present the results of a detailed study of vertical surface brightness profiles of edge-on disk galaxies. Although the exponential disk scale height is constant to first order approximation, we show that for the large majority of galaxies in our sample, the scale height increases with distance al

  12. The opacity of spiral galaxy disks V. Dust opacity, HI distributions and sub-mm emission

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    The opacity of spiral galaxy disks, from counts of distant galaxies, is compared to HI column densities. The opacity measurements are calibrated using the "Synthetic Field Method" from Gonzalez et al. (1998, ApJ, 506, 152), Holwerda et al. (2005a, AJ, 129, 1381). When compared for individual disks,

  13. Near-Infrared Structure of Fast and Slow Rotating Disk Galaxies

    CERN Document Server

    Schechtman-Rook, Andrew

    2014-01-01

    We investigate the stellar disk structure of six nearby edge-on spiral galaxies using high-resolution JHKs-band images and 3D radiative transfer models. To explore how mass and environment shape spiral disks, we selected galaxies with rotational velocities between 69 150 km/sec) galaxies, only NGC 4013 has the super-thin+thin+thick nested disk structure seen in NGC 891 and the Milky Way, albeit with decreased oblateness, while NGC 1055, a disturbed massive spiral galaxy, contains disks with hz $\\lesssim$ 200 pc. NGC 4565, another fast-rotator, contains a prominent ring at a radius ~5 kpc but no super-thin disk. Despite these differences, all fast-rotating galaxies in our sample have inner truncations in at least one of their disks. These truncations lead to Freeman Type II profiles when projected face-on. Slow-rotating galaxies are less complex, lacking inner disk truncations and requiring fewer disk components to reproduce their light distributions. Super-thin disk components in undisturbed disks contribute...

  14. Star formation and turbulent dissipation in models of disk galaxy evolution

    CERN Document Server

    Avila-Reese, V; Vázquez-Semadeni, E

    2003-01-01

    The kinetic energy dissipation rate in the turbulent ISM of disk galaxies is a key ingredient in galaxy evolution models since it determines the effectiveness of large-scale star formation (SF) feedback. Using magneto-hydro-dynamic simulations, we find that the ISM dissipates efficiently the turbulent kinetic energy injected by sources of stellar nature. Thus, the SF process may be self-regulated by an energy balance only at the level of the disk ISM. The use of the self-regulation SF mechanism in galaxy evolutionary models, where disks form inside growing Cold Dark Matter halos, allows to predict the SF history of disk galaxies, including the Milky Way and the solar neighborhood, as well as the contribution of the whole population of disk galaxies to the cosmic SF history. The results are encouraging.

  15. The inner regions of disk galaxies: a constant baryonic fraction?

    CERN Document Server

    Lelli, Federico

    2014-01-01

    For disk galaxies (spirals and irregulars), the inner circular-velocity gradient (inner steepness of the rotation curve) correlates with the central surface brightness with a slope of ~0.5. This implies that the central dynamical mass density scales almost linearly with the central baryonic density. Here I show that this empirical relation is consistent with a simple model where the central baryonic fraction f_bar(0) is fixed to 1 (no dark matter) and the observed scatter is due to differences in the baryonic mass-to-light ratio M_bar/L (ranging from 1 to 3 in the R-band) and in the characteristic thickness of the central stellar component dz (ranging from 100 to 500 pc). Models with lower baryonic fractions are possible, although they require some fine-tuning in the values of M_bar/L and dz. Regardless of the actual value of f_bar(0), the fact that different types of galaxies do not show strong variations in f_bar(0) is surprising, and may represent a challenge for models of galaxy formation in a LCDM cosmol...

  16. Molecular Gas and Star Formation in Nearby Disk Galaxies

    CERN Document Server

    Leroy, Adam K; Sandstrom, Karin; Schruba, Andreas; Munoz-Mateos, Juan-Carlos; Bigiel, Frank; Bolatto, Alberto; Brinks, Elias; de Blok, W J G; Meidt, Sharon; Rix, Hans-Walter; Rosolowsky, Erik; Schinnerer, Eva; Schuster, Karl-Friedrich; Usero, Antonio

    2013-01-01

    We compare molecular gas traced by 12CO(2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between Sig_mol and Sig_SFR but also find important second-order systematic variations in the apparent molecular gas depletion time, t_dep^mol = Sig_mol / Sig_SFR. At our 1 kpc common resolution, CO correlates closely with many tracers of the recent SFR. Weighting each line of sight equally and using a fixed, Milky Way alpha_CO, our data yield a molecular gas depletion time, t_dep^mol=Sig_mol/Sig_SFR ~ 2.2 Gyr with 0.3 dex scatter, in good agreement with literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density and find N=1+/-0.15 for our full data set with some variation from galaxy to galaxy. However, we caution that a power law treatment oversimplifies the topic given that we observe correlat...

  17. The Inner Regions of Disk Galaxies: A Constant Baryonic Fraction?

    Directory of Open Access Journals (Sweden)

    Federico Lelli

    2014-07-01

    Full Text Available For disk galaxies (spirals and irregulars, the inner circular-velocity gradient dRV0 (inner steepness of the rotation curve correlates with the central surface brightness ∑*,0 with a slope of ~0.5. This implies that the central dynamical mass density scales almost linearly with the central baryonic density. Here I show that this empirical relation is consistent with a simple model where the central baryonic fraction ƒbar,0 is fixed to 1 (no dark matter and the observed scatter is due to differences in the baryonic mass-to-light ratio Mbar / LR (ranging from 1 to 3 in the R-band and in the characteristic thickness of the central stellar component Δz (ranging from 100 to 500 pc. Models with lower baryonic fractions are possible, although they require some fine-tuning in the values of Mbar/LR and Δz. Regardless of the actual value of ƒbar,0, the fact that different types of galaxies do not show strong variations in ƒbar,0 is surprising, and may represent a challenge for models of galaxy formation in a Λ Cold Dark Matter (ΛCDM cosmology.

  18. Galaxy And Mass Assembly: Deconstructing Bimodality - I. Red ones and blue ones

    OpenAIRE

    Taylor, Edward N.; Hopkins, Andrew M; Baldry, Ivan K.; Bland-Hawthorn, Joss; Brown, Michael J. I.; Colless, Matthew; Driver, Simon; Norberg, Peder; Robotham, Aaron S G; Alpaslan, Mehmet; Brough, Sarah; Cluver, Michelle E.; Gunawardhana, Madusha; Kelvin, Lee S; Liske, Jochen

    2014-01-01

    We measure the mass functions for generically red and blue galaxies, using a z 8.7 field galaxies from the Galaxy And Mass Assembly (GAMA) survey. Our motivation is that, as we show, the dominant uncertainty in existing measurements stems from how 'red' and 'blue' galaxies have been selected/defined. Accordingly, we model our data as two naturally overlapping populations, each with their own mass function and colour-mass relation, which enables us characterise the tw...

  19. HI Gas in Disk and Dwarf Galaxies in the Semi-analytic Models of Galaxy Formation†

    Science.gov (United States)

    Fu, Jian; Wang, Jing; Luo, Yu

    We construct the radially-resolved semi-analytic models of galaxy formation based on the L-Galaxies model framework, which include both atomic and molecular gas phase in ISM. The models run on the halo outputs of ΛCDM cosmology N-body simulation. Our models can reproduce varies observations of HI gas in nearby galaxies, e.g. the HI mass function, the HI-to-star ratio vs stellar mass and stellar surface density, universal HI radial surface density profile in outer disks etc. We also give the physical origin of HI size-mass relation. Based on our model results for local dwarf galaxies, we show that the ``missing satellite problem'' also exists in the HI component, i.e., the models over-predict dwarf galaxies with low HI mass around the Milky Way. That is a shortcoming of current ΛCDM cosmology framework. Future survey for HI gas in local dwarf galaxies (e.g. MeerKAT, SKA & FAST) can help to verify the nature of dark matter (cold or warm).

  20. The Mid-Infrared Properties of Blue Compact Dwarf Galaxies

    CERN Document Server

    Yanling Wu; Houck, J R; Bernasrd-Salas, J; Lebouteiller, V

    2008-01-01

    The unprecedented sensitivity of the Spitzer Space Telescope has enabled us for the first time to detect a large sample of Blue Compact Dwarf galaxies (BCDs), which are intrinsically faint in the infrared. In the present paper we present a summary of our findings which providing essential information on the presence/absence of the Polycyclic Aromatic Hydrocarbon features in metal-poor environments. In addition, using Spitzer/IRS high-resolution spectroscopy, we study the elemental abundances of neon and sulfur in BCDs and compare with the results from optical studies. Finally, we present an analysis of the mid- and far-infrared to radio correlation in low luminosity low metallicity galaxies.

  1. The environment of nearby Blue Compact Dwarf Galaxies

    CERN Document Server

    Lopez-Sanchez, Angel R; van Eymeren, Janine; Esteban, Cesar; Popping, Attila; Hibbard, John

    2009-01-01

    We are obtaining deep multiwavelength data of a sample of nearby blue compact dwarf galaxies (BCDGs) combining broad-band optical/NIR and H$\\alpha$ photometry, optical spectroscopy and 21-cm radio observations. Here we present HI results obtained with the Australia Telescope Compact Array for some BCDGs, all showing evident interaction features in their neutral gas component despite the environment in which they reside. Our analysis strongly suggests that interactions with or between low-luminosity dwarf galaxies or HI clouds are the main trigger mechanism of the star-forming bursts in BCDGs; however these dwarf objects are only detected when deep optical images and complementary HI observations are performed. Are therefore BCDGs real isolated systems?

  2. The Fate of Luminous Compact Blue Galaxies: An Environmental Approach

    CERN Document Server

    Crawford, S M; Glenn, A; Hössel, J G

    2004-01-01

    Luminous Compact Blue Galaxies (LCBGs) are a heterogeneous class which dominate an intermediate phase of galaxy evolution. These sources account for the majority of the star formation between 0.3

  3. Detection of Prominent Stellar Disks in the Progenitors of Present-day Massive Elliptical Galaxies

    Science.gov (United States)

    Davari, Roozbeh H.; Ho, Luis C.; Mobasher, Bahram; Canalizo, Gabriela

    2017-02-01

    Massive galaxies at high redshifts (z > 2) show different characteristics from their local counterparts: they are compact and most likely have a disk. In this study, we trace the evolution of local massive galaxies by performing a detailed morphological analysis, namely, fitting single Sérsic profiles and performing bulge+disk decompositions. We analyze ∼250 massive galaxies selected from all CANDELS fields (COSMOS, UDS, EGS, GOODS-South, and GOODS-North). We confirm that both star-forming and quiescent galaxies increase their sizes significantly from z ≈ 2.5 to the present day. The global Sérsic index of quiescent galaxies increases over time (from n ≈ 2.5 to n > 4), while that of star-forming galaxies remains roughly constant (n ≈ 2.5). By decomposing galaxy profiles into bulge+disk components, we find that massive galaxies at high redshift have prominent stellar disks, which are also evident from visual inspection of the images. By z ≈ 0.5, the majority of the disks disappear and massive quiescent galaxies begin to resemble the local elliptical galaxies. Star-forming galaxies have lower bulge-to-total ratios (B/T) than their quiescent counterparts in each redshift bin. The bulges of star-forming and quiescent galaxies follow different evolutionary histories, while their disks evolve similarly. Based on our morphological analysis and previous cosmological simulations, we argue that major mergers, along with minor mergers, have played a crucial role in the significant increase in size of high-z galaxies and the destruction of their massive and large-scale disks.

  4. What will blue compact dwarf galaxies evolve into?

    CERN Document Server

    Meyer, Hagen T; Janz, Joachim; Papaderos, Polychronis

    2013-01-01

    We present and analyse the photometric properties of a nearly complete sample of blue compact dwarf (BCD) and irregular galaxies in the Virgo cluster from multi-band SDSS images. Our study intends to shed light on the ongoing debate of whether a structural evolution from present-day star-forming dwarf galaxies in a cluster environment into ordinary early-type dwarf galaxies is possible based on the structural properties. For this purpose, we decompose the surface brightness profiles of the BCDs into the luminosity contribution of the starburst component and that of their underlying low surface brightness (LSB) host. The latter dominates the stellar mass of the BCD. We find that the LSB-components of the Virgo BCDs are structurally compatible with the more compact half of the Virgo early-type dwarfs, except for a few extreme BCDs. Thus, after termination of starburst activity, the BCDs will presumably fade into galaxies that are structurally similar to ordinary early-type dwarfs. In contrast, the irregulars ar...

  5. Hot Dust Obscured Galaxies with Excess Blue Light: Dual AGN or Single AGN Under Extreme Conditions?

    Science.gov (United States)

    Assef, R. J.; Walton, D. J.; Brightman, M.; Stern, D.; Alexander, D.; Bauer, F.; Blain, A. W.; Diaz-Santos, T.; Eisenhardt, P. R. M.; Finkelstein, S. L.; Hickox, R. C.; Tsai, C.-W.; Wu, J. W.

    2016-03-01

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13-050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M⊙ yr-1. Deep polarimetry observations could confirm the reflection hypothesis.

  6. HOT DUST OBSCURED GALAXIES WITH EXCESS BLUE LIGHT: DUAL AGN OR SINGLE AGN UNDER EXTREME CONDITIONS?

    Energy Technology Data Exchange (ETDEWEB)

    Assef, R. J.; Diaz-Santos, T. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Walton, D. J.; Brightman, M. [Space Radiation Laboratory, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D.; Eisenhardt, P. R. M.; Tsai, C.-W. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-236, Pasadena, CA 91109 (United States); Alexander, D. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Bauer, F. [Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 22 (Chile); Blain, A. W. [Physics and Astronomy, University of Leicester, 1 University Road, Leicester LE1 7RH (United Kingdom); Finkelstein, S. L. [The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Wu, J. W., E-mail: roberto.assef@mail.udp.cl [UCLA Astronomy, P.O. Box 951547, Los Angeles, CA 90095-1547 (United States)

    2016-03-10

    Hot dust-obscured galaxies (Hot DOGs) are a population of hyper-luminous infrared galaxies identified by the Wide-field Infrared Survey Explorer (WISE) mission from their very red mid-IR colors, and characterized by hot dust temperatures (T > 60 K). Several studies have shown clear evidence that the IR emission in these objects is powered by a highly dust-obscured active galactic nucleus (AGN) that shows close to Compton-thick absorption at X-ray wavelengths. Thanks to the high AGN obscuration, the host galaxy is easily observable, and has UV/optical colors usually consistent with those of a normal galaxy. Here we discuss a sub-population of eight Hot DOGs that show enhanced rest-frame UV/optical emission. We discuss three scenarios that might explain the excess UV emission: (i) unobscured light leaked from the AGN by reflection over the dust or by partial coverage of the accretion disk; (ii) a second unobscured AGN in the system; or (iii) a luminous young starburst. X-ray observations can help discriminate between these scenarios. We study in detail the blue excess Hot DOG WISE J020446.13–050640.8, which was serendipitously observed by Chandra/ACIS-I for 174.5 ks. The X-ray spectrum is consistent with a single, hyper-luminous, highly absorbed AGN, and is strongly inconsistent with the presence of a secondary unobscured AGN. Based on this, we argue that the excess blue emission in this object is most likely either due to reflection or a co-eval starburst. We favor the reflection scenario as the unobscured star formation rate needed to power the UV/optical emission would be ≳1000 M{sub ⊙} yr{sup −1}. Deep polarimetry observations could confirm the reflection hypothesis.

  7. In-spiraling Clumps in Blue Compact Dwarf Galaxies

    CERN Document Server

    Elmegreen, Bruce G; Hunter, Deidre

    2012-01-01

    Giant star-formation clumps in dwarf irregular galaxies can have masses exceeding a few percent of the galaxy mass enclosed inside their orbital radii. They can produce sufficient torques on dark matter halo particles, halo stars, and the surrounding disk to lose their angular momentum and spiral into the central region in 1 Gyr. Pairs of giant clumps with similarly large relative masses can interact and exchange angular momentum to the same degree. The result of this angular momentum loss is a growing central concentration of old stars, gas, and star formation that can produce a long-lived starburst in the inner region, identified with the BCD phase. This central concentration is proposed to be analogous to the bulge in a young spiral galaxy. Observations of star complexes in five local BCDs confirm the relatively large clump masses that are expected for this process. The observed clumps also seem to contain old field stars, even after background light subtraction, in which case the clumps may be long-lived....

  8. Role of disk galaxies in the chemical enrichment of the intracluster medium

    CERN Document Server

    Wiebe, D S; Tutukov, A V

    1999-01-01

    Elliptical galaxies are often assumed to be the primary source of heavy elements in the intracluster medium (ICM), with the contribution of other morphological types being negligible. In this paper we argue that a role of spiral galaxies in the chemical evolution of the ICM is also important. This statement rests upon our recent calculations of the heavy element loss from a disk galaxy through the hot steady-state galactic wind and dust grains expulsion by stellar radiation pressure. We show that a typical disk galaxy is nearly as effective in enriching the ICM as an elliptical galaxy of the same mass. Having estimated the oxygen and iron loss from a single galaxy, we integrate them over the galactic mass spectrum. We show that the "effective" loss (per unit luminosity) from spiral galaxies is comparable to the loss from ellipticals. The dominant role of early-type galaxies in rich clusters is caused by that they outnumber spirals.

  9. On the generation of asymmetric warps in disk galaxies

    CERN Document Server

    Saha, K; Saha, Kanak; Jog, Chanda J.

    2005-01-01

    The warps in many spiral galaxies are now known to asymmetric. Recent sensitive observations have revealed that asymmetry of warps may be the norm rather than exception. However there exists no generic mechanism to generate these asymmetries in warps. We have derived the dispersion relation in a compact form for the S-shaped warps(described by the m=1 mode) and the bowl-shaped distribution(described by the m=0 mode) in galactic disk embedded in a dark matter halo. We then performed the numerical modal analysis and used the linear and time-dependent superposition principle to generate asymmetric warps in the disk. On doing the modal analysis we find the frequency of the $m=0$ mode is much larger than that of the $m=1$ mode. The linear and time-dependent superposition of these modes with their unmodulated amplitudes(that is, the coefficients of superposition being unity) results in an asymmetry in warps of ~ 20 - 40 %, whereas a smaller coefficient for the m=0 mode results in a smaller asymmetry. The resulting ...

  10. FORMATION OF ULTRA-COMPACT BLUE DWARF GALAXIES AND THEIR EVOLUTION INTO NUCLEATED DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Bekki, Kenji [ICRAR, M468, The University of Western Australia 35 Stirling Highway, Crawley Western Australia, 6009 (Australia)

    2015-10-10

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf–dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf–dwarf mergers. We find that the remnants of dwarf–dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z ∼ [0.2–1]Z{sub ⊙}). We also find that the remnants of these mergers can have rather high mass densities (10{sup 4} M{sub ⊙} pc{sup −3}) within the central 10 pc and small half-light radii (40−100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R < 100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multiple stellar populations with different ages and metallicities. These very compact blue remnants can be identified as UCBDs soon after merging and as nucleated dwarfs after the young stars fade. We discuss these results in the context of the origins of metal-rich ultra-compact dwarfs and SGNs.

  11. Comparing the Evolution of the Galaxy Disk Sizes with CDM Models The Hubble Deep Field

    CERN Document Server

    Giallongo, E; Poli, F; D'Odorico, S; Fontana, A

    2000-01-01

    The intrinsic sizes of the field galaxies with I-19) galaxies is skewed with respect to the CDM predictions and an excess of small-size disks (R_d<2 kpc) is already present at z~ 0.5. The excess persists up to z~3 and involves brighter galaxies . Such an excess may be reduced if luminosity-dependent effects, like starburst activity in interacting galaxies, are included in the physical mechanisms governing the star formation history in CDM models.

  12. 3D Spectroscopy of Blue Compact Galaxies. Diagnostic Diagrams

    CERN Document Server

    Martinez-Delgado, I; Muñoz-Tunón, C; Moiseev, A V; Cairos, L M; Martinez-Delgado, Ismael; Tenorio-Tagle, Guillermo; Munoz-Tunon, Casiana; Moiseev, Alexei V.; Cairos, Luz M.

    2007-01-01

    Here we present the analysis of 3D spectroscopic data of three Blue Compact Galaxies (Mrk324, Mrk370, and IIIZw102). Each of the more than 22500 spectra obtained for each galaxy has been fitted by a single gaussian from which we have inferred the velocity dispersion (sigma), the peak intensity (Ipeak), and the central wavelength (lambda_c). The analysis shows that the sigma vs Ipeak diagrams look remarkably similar to those obtained for giant extragalactic HII regions. They all present a supersonic narrow horizontal band that extends across all the range of intensities and that result from the massive nuclear star-forming regions of every galaxy. The sigma vs Ipeak diagrams present also several inclined bands of lower intensity and an even larger sigma, arising from the large galactic volumes that surround the main central emitting knots. Here we also show that the sigma vs lambda_c and lambda_c vs Ipeak diagrams, are powerful tools able to unveil the presence of high and low mass stellar clusters, and thus a...

  13. A High-Velocity Collision With Our Galaxy's Disk

    Science.gov (United States)

    Kohler, Susanna

    2016-08-01

    What caused the newly discovered supershell in the outskirts of our galaxy? A new study finds evidence that a high-velocity cloud may have smashed into the Milky Ways disk millions of years ago.Mysterious Gas ShellsA single velocity-channel map of the supershell GS040.2+00.670, with red contours marking the high-velocity cloud at its center. [Adapted from Park et al. 2016]The neutral hydrogen gas that fills interstellar space is organized into structures like filaments, loops, and shells. Supershells are enormous shells of hydrogen gas that can have radii of a thousand light-years or more; weve spotted about 20 of these in our own galaxy, and more in nearby dwarfs and spiral galaxies.How do these structures form? One theory is that they result from several supernovae explosions occurring in the same area. But the energy needed to create a supershell is more than 3 x 1052 erg, which corresponds to over 30 supernovae quite a lot to have exploding in the same region.Theres an interesting alternative scenario: the supershells might instead be caused by the impacts of high-velocity clouds that fall into the galactic disk.Velocity data for the compact high-velocity cloud CHVC040. The cloud is moving fast enough to create the supershell observed. [Adapted from Park et al. 2016]The Milky Ways Speeding CloudsHigh-velocity clouds are clouds of mostly hydrogen that speed through the Milky Way with radial velocities that are very different from the material in the galactic disk. The origins of these clouds are unknown, but its proposed that they come from outside the galaxy they might be fragments of a nearby, disrupting galaxy, or they might have originated from flows of accreting gas in the space in between galaxies.Though high-velocity clouds have long been on the list of things that might cause supershells, weve yet to find conclusive evidence of this. But that might have just changed, with a recent discovery by a team of scientists led by Geumsook Park (Seoul National

  14. The spectacular 200 kpc-wide disk of the Malin 1 giant low surface brightness galaxy

    Science.gov (United States)

    Boissier, Samuel

    2017-03-01

    Malin 1 is the best example among giant low surface brightness galaxies. New observations of this object in 6 broad-bands allow us for the first time to perform a pan-chromatic study of the stellar population in its 200 kpc wide disk. We observe a spiral structure revealing a star forming disk. The colors indicate a long history with a low efficiency of star formation. It is well reproduced by a model of disk galaxy making it similar to the disk of the Milky Way or other nearby spirals, except for its extremely large angular momentum.

  15. Bars in Disk-Dominated and Bulge-Dominated Galaxies at z~0: New Insights from ~3600 SDSS Galaxies

    CERN Document Server

    Barazza, Fabio D; Marinova, Irina

    2007-01-01

    We present a study of large-scale bars in the local Universe, based on a large sample of ~3692 galaxies, with -18.5 60^{\\circ}$) systems, we find the following results. (1) The optical r-band fraction (f_opt-r) of barred galaxies, when averaged over the whole sample, is ~48%-52%. (2)~When galaxies are separated according to half light radius (r_e), or normalized r_e/R_24, which is a measure of the bulge-to-disk (B/D) ratio, a remarkable result is seen: f_opt-r rises sharply, from ~40% in galaxies that have small r_e/R_24 and visually appear to host prominent bulges, to ~70% for galaxies that have large r_e/R_24 and appear disk-dominated. (3)~f_opt-r rises for galaxies with bluer colors, lower masses, or fainter luminosities. (4) While hierarchical $\\Lambda$CDM models of galaxy evolution models fail to produce galaxies without classical bulges, our study finds that ~20% of disk galaxies appear to be ``quasi-bulgeless''. (5) After applying the same cutoffs in magnitude (M_V= 1.5 kpc), and bar ellipticity (e_bar...

  16. Significant enhancement of ${\\rm H_2}$ formation in disk galaxies under strong ram pressure

    CERN Document Server

    Henderson, Benjamin

    2016-01-01

    We show, for the first time, that ${\\rm H_2}$ formation on dust grains can be enhanced in disk galaxies under strong ram-pressure (RP). We numerically investigate how the time evolution, of ${\\rm H}$ {\\sc i} and ${\\rm H_2}$ components in disk galaxies orbiting a group/cluster of galaxies, can be influenced by hydrodynamical interaction between the gaseous components of the galaxies and the hot intra-cluster medium (ICM). We find that compression of ${\\rm H}$ {\\sc i} caused by RP increases ${\\rm H_2}$ formation in disk galaxies, before RP rapidly strips ${\\rm H}$ {\\sc i}, cutting off the fuel supply and causing a drop in ${\\rm H_2}$ density. We also find that the level of this ${\\rm H_2}$ formation enhancement in a disk galaxy under RP depends on the mass of its host cluster dark matter (DM) halo, initial positions and velocities of the disk galaxy, and disk inclination angle with respect to the orbital plane. We demonstrate that dust growth is a key factor in the evolution of the ${\\rm H}$ {\\sc i} and ${\\rm H...

  17. Sustaining star formation rates in spiral galaxies - Supernova-driven turbulent accretion disk models applied to THINGS galaxies

    CERN Document Server

    Vollmer, B

    2010-01-01

    Gas disks of spiral galaxies can be described as clumpy accretion disks without a coupling of viscosity to the actual thermal state of the gas. The model description of a turbulent disk consisting of emerging and spreading clumps (Vollmer & Beckert 2003) contains free parameters, which can be constrained by observations of molecular gas, atomic gas and the star formation rate for individual galaxies. Radial profiles of 18 nearby spiral galaxies from THINGS, HERACLES, SINGS, and GALEX data are used to compare the observed star formation efficiency, molecular fraction, and velocity dispersion to the model. The observed radially decreasing velocity dispersion can be reproduced by the model. In the framework of this model the decrease in the inner disk is due to the stellar mass distribution which dominates the gravitational potential. Introducing a radial break in the star formation efficiency into the model improves the fits significantly. This change in star formation regime is realized by replacing the fr...

  18. MOLECULAR GAS AND STAR FORMATION IN NEARBY DISK GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Leroy, Adam K.; Munoz-Mateos, Juan-Carlos [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Walter, Fabian; Sandstrom, Karin; Meidt, Sharon; Rix, Hans-Walter; Schinnerer, Eva [Max Planck Institute fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany); Schruba, Andreas [California Institute for Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Bigiel, Frank [Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Bolatto, Alberto [Department of Astronomy, University of Maryland, College Park, MD (United States); Brinks, Elias [Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); De Blok, W. J. G. [Astrophysics, Cosmology and Gravity Centre, Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Rosolowsky, Erik [University of British Columbia, Okanagan Campus, Kelowna, BC (Canada); Schuster, Karl-Friedrich [IRAM, 300 rue de la Piscine, F-38406 St. Martin d' Heres (France); Usero, Antonio [Observatorio Astronomico Nacional, C/ Alfonso XII, 3, E-28014 Madrid (Spain)

    2013-08-01

    We compare molecular gas traced by {sup 12}CO (2-1) maps from the HERACLES survey, with tracers of the recent star formation rate (SFR) across 30 nearby disk galaxies. We demonstrate a first-order linear correspondence between {Sigma}{sub mol} and {Sigma}{sub SFR} but also find important second-order systematic variations in the apparent molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}. At the 1 kpc common resolution of HERACLES, CO emission correlates closely with many tracers of the recent SFR. Weighting each line of sight equally, using a fixed {alpha}{sub CO} equivalent to the Milky Way value, our data yield a molecular gas depletion time, {tau}{sub dep}{sup mol}={Sigma}{sub mol}/{Sigma}{sub SFR}{approx}2.2 Gyr with 0.3 dex 1{sigma} scatter, in very good agreement with recent literature data. We apply a forward-modeling approach to constrain the power-law index, N, that relates the SFR surface density and the molecular gas surface density, {Sigma}{sub SFR}{proportional_to}{Sigma}{sub mol}{sup N}. We find N = 1 {+-} 0.15 for our full data set with some scatter from galaxy to galaxy. This also agrees with recent work, but we caution that a power-law treatment oversimplifies the topic given that we observe correlations between {tau}{sub dep}{sup mol} and other local and global quantities. The strongest of these are a decreased {tau}{sub dep}{sup mol} in low-mass, low-metallicity galaxies and a correlation of the kpc-scale {tau}{sub dep}{sup mol} with dust-to-gas ratio, D/G. These correlations can be explained by a CO-to-H{sub 2} conversion factor ({alpha}{sub CO}) that depends on dust shielding, and thus D/G, in the theoretically expected way. This is not a unique interpretation, but external evidence of conversion factor variations makes this the most conservative explanation of the strongest observed {tau}{sub dep}{sup mol} trends. After applying a D/G-dependent {alpha}{sub CO}, some weak correlations between {tau}{sub dep

  19. Supermassive black holes do not correlate with galaxy disks or pseudobulges.

    Science.gov (United States)

    Kormendy, John; Bender, R; Cornell, M E

    2011-01-20

    The masses of supermassive black holes are known to correlate with the properties of the bulge components of their host galaxies. In contrast, they seem not to correlate with galaxy disks. Disk-grown 'pseudobulges' are intermediate in properties between bulges and disks; it has been unclear whether they do or do not correlate with black holes in the same way that bulges do. At stake in this issue are conclusions about which parts of galaxies coevolve with black holes, possibly by being regulated by energy feedback from black holes. Here we report pseudobulge classifications for galaxies with dynamically detected black holes and combine them with recent measurements of velocity dispersions in the biggest bulgeless galaxies. These data confirm that black holes do not correlate with disks and show that they correlate little or not at all with pseudobulges. We suggest that there are two different modes of black-hole feeding. Black holes in bulges grow rapidly to high masses when mergers drive gas infall that feeds quasar-like events. In contrast, small black holes in bulgeless galaxies and in galaxies with pseudobulges grow as low-level Seyfert galaxies. Growth of the former is driven by global processes, so the biggest black holes coevolve with bulges, but growth of the latter is driven locally and stochastically, and they do not coevolve with disks and pseudobulges.

  20. Properties of Galaxy Disks in Hierarchical Hydrodynamical Simulations Comparison with Observational Data

    CERN Document Server

    Saiz, A; Tissera, P B; Courteau, S

    2001-01-01

    We analyze the structural and dynamical properties of disk-like objects formed in fully consistent cosmological simulations with an inefficient star formation algorithm. Comparison with data of similar observable properties of spiral galaxies gives satisfactory agreement.

  1. MCMC Analysis of biases in the interpretation of disk galaxy kinematics

    Science.gov (United States)

    Aquino-Ortíz, E.; Valenzuela, O.; Cano-Díaz, M.; Sánchez-Sánchez, S. F.; Hernández-Toledo, H.

    2016-06-01

    The new generation of galaxy surveys like SAMI, CALIFA and MaNGA opens up the possibility of studying simultaneously properties of galaxies such as spiral arms, bars, disk geometry and orientation, stellar and gas mass distribution, 2D kinematics, etc. The previous task involves exploring a complicated multi-dimensional parameter space. Puglielli et al. (2010) introduced Bayesian statistics and MCMC (Monte Carlo Markov Chain) techniques to construct dynamical models of spiral galaxies. In our study we used synthetic velocity fields that include non-circular motions and assume different disk orientations in order to produce mock observations. We apply popular reconstruction techniques in order to estimate the geometrical disk parameters, systemic velocities, rotation curve shape and maximum circular velocity which are crucial to construct the scaling relations. We conclude that a detailed analysis of kinematics in galaxies using MCMC technique will be reflected in accurate estimations of galaxy properties and more robust scalings relations, otherwise physical conclusions may be importantly biased.

  2. The opacity of Spiral Disks IV : Radial Extinction Profiles from Counts of Distant Galaxies seen through Foreground Disks

    NARCIS (Netherlands)

    Holwerda, B. W.; González, R. A.; Allen, R. J.; Kruit, P.C. van der

    2004-01-01

    Dust extinction can be determined from the number of distant field galaxies seen through a spiral disk. To calibrate this number for the crowding and confusion introduced by the foreground image, Gonzalez et al. (1998) and Holwerda et al. (2005a) developed the ``Synthetic Field Method'' (SFM), which

  3. The opacity of spiral galaxy disks. VIII. Structure of the cold ISM

    NARCIS (Netherlands)

    Holwerda, B. W.; Draine, B.; Gordon, K. D.; Gonzalez, R. A.; Calzetti, D.; Thornley, M.; Buckalew, B.; Allen, Ronald J.; van der Kruit, P. C.

    2007-01-01

    The quantity of dust in a spiral disk can be estimated using the dust's typical emission or the extinction of a known source. In this paper we compare two techniques, one based on emission and one on absorption, applied to sections of 14 disk galaxies. The two measurements reflect, respectively, the

  4. The opacity of spiral galaxy disks VI. Extinction, stellar light and color

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; van der Kruit, PC; Allen, RJ

    2005-01-01

    In this paper we explore the relation between dust extinction and stellar light distribution in disks of spiral galaxies. Extinction influences our dynamical and photometric perception of disks, since it can distort our measurement of the contribution of the stellar component. To characterize the to

  5. The Opacity of Spiral Galaxy Disks III : Automating the "Synthetic Field Method"

    NARCIS (Netherlands)

    Holwerda, B. W.; González, R. A.; Allen, R. J.; Kruit, P. C. van der

    2004-01-01

    Abstract: The dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. (1998) developed a method for this calibrat

  6. The DiskMass Survey. VII. The distribution of luminous and dark matter in spiral galaxies

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present dynamically-determined rotation-curve mass decompositions of 30 spiral galaxies, which were carried out to test the maximum-disk hypothesis and to quantify properties of their dark-matter halos. We used measured vertical velocity dispersions of the disk stars to calculate dynamical mass s

  7. Why do disk galaxies present a common gas-phase metallicity gradient?

    Science.gov (United States)

    Chang, R.; Zhang, Shuhui; Shen, Shiyin; Yin, Jun; Hou, Jinliang

    2017-03-01

    CALIFA data show that isolated disk galaxies present a common gas-phase metallicity gradient, with a characteristic slope of -0.1dex/re between 0.3 and 2 disk effective radius re (Sanchez et al. 2014). Here we construct a simple model to investigate which processes regulate the formation and evolution.

  8. The opacity of spiral galaxy disks. III. Automating the synthetic field method

    NARCIS (Netherlands)

    Holwerda, BW; Gonzalez, RA; Allen, RJ; van der Kruit, PC

    2005-01-01

    Dust extinction in spiral disks can be estimated from the counts of background field galaxies, provided the deleterious effects of confusion introduced by structure in the image of the foreground spiral disk can be calibrated. Gonzalez et al. developed a method for this calibration, the Synthetic Fi

  9. Comparison between Disk-like Objects Formed in Hierarchical Hydrodynamical Simulations and Observations of Spiral Galaxies

    CERN Document Server

    Saiz, A; Tissera, P B; Courteau, S

    2001-01-01

    We analyze the structural and dynamical properties of disk-like objects formed in fully consistent cosmological simulations which include inefficient star formation. Comparison with data of similar observable properties of spiral galaxies gives satisfactory agreement, in contrast with previous findings using other codes. This suggests that the stellar formation implementation used has allowed the formation of disks as well as guaranteed their stability.

  10. Stellar disk truncations at high z : Probing inside-out galaxy formation

    NARCIS (Netherlands)

    Trujillo, [No Value; Pohlen, M

    2005-01-01

    We have conducted a systematic search for stellar disk truncations in disklike galaxies at intermediate redshift (z <1.1) using the Hubble Ultra Deep Field data. We use the position of the truncation as a direct estimator of the size of the stellar disk. After accounting for the surface brightness e

  11. Effect of halo component on bar-formation in disk galaxies

    Science.gov (United States)

    Hohl, F.

    1975-01-01

    Numerical experiments are performed to determine the effect of a fixed halo component of mass on the stability of purely stellar disks. The rotation curve of the fixed halo component corresponds to the Schmidt model of the galaxy. It is found that when the stellar disk contains less than 50% of the total mass, the large-scale bar-making instability is effectively suppressed. For disks containing 50% or more of the total mass, a bar structure quickly forms.

  12. Cepheid Variables in the Flared Outer Disk of our Galaxy

    CERN Document Server

    Feast, Michael W; Matsunaga, Noriyuki; Whitelock, Patricia A

    2014-01-01

    Flaring and warping of the disk of the Milky Way have been inferred from observations of atomic hydrogen, but stars associated with flaring have not hitherto been reported. In the area beyond the Galactic centre the stars are largely hidden from view by dust, and the kinematic distances of the gas cannot be estimated. Thirty-two possible Cepheid stars (young pulsating variable stars) in the direction of the Galactic bulge were recently identified. With their well-calibrated period-luminosity relationships, Cepheid stars are useful distance indicators. When observations of these stars are made in two colours, so that their distance and reddening can be determined simultaneously, the problems of dust obscuration are minimized. Here we report that five of the candidates are classical Cepheid stars. These five stars are distributed from approximately one to two kiloparsecs above and below the plane of the Galaxy, at radial distances of about 13 to 22 kiloparsecs from the centre. The presence of these relatively y...

  13. Dynamics of Non-Steady Spiral Arms in Disk Galaxies

    CERN Document Server

    Baba, Junichi; Wada, Keiichi

    2012-01-01

    In order to understand the physical mechanisms underlying non-steady stellar spiral arms in disk galaxies, we analyzed the growing and damping phases of their spiral arms using three-dimensional $N$-body simulations. We confirmed that the spiral arms are formed due to a swing amplification mechanism that reinforces density enhancement as a seeded wake. In the damping phase, the Coriolis force exerted on a portion of the arm surpasses the gravitational force that acts to shrink the portion. Consequently, the stars in the portion escape from the arm, and subsequently they form a new arm at a different location. The time-dependent nature of the spiral arms are originated in the continual repetition of this non-linear phenomenon. Since a spiral arm does not rigidly rotate, but follows the galactic differential rotation, the stars in the arm rotate at almost the same rate as the arm. In other words, every single position in the arm can be regarded as the co-rotation point. Due to interaction with their host arms, ...

  14. Detection of Prominent Stellar Disks in the Progenitors of Present-day Massive Elliptical Galaxies

    CERN Document Server

    Davari, Roozbeh H; Mobasher, Bahram; Canalizo, Gabriela

    2016-01-01

    Massive galaxies at higher redshifts ($\\emph{z}$ $>$ 2) show different characteristics from their local counterparts: They are compact and most likely have a disk. In this study, we trace the evolution of local massive galaxies by performing a detailed morphological analysis, namely, fitting single S\\'{e}rsic profiles and performing bulge+disk decompositions. We analyze $\\sim$ 250 massive galaxies selected from all CANDELS fields (COSMOS, UDS, EGS, GOODS-South and GOODS-North). We confirm that both star-forming and quiescent galaxies increase their sizes significantly from $\\emph{z}$ $\\approx$ 2.5 to the present day. The global S\\'{e}rsic index of quiescent galaxies increases over time (from $n$ $\\approx$ 2.5 to $n$ $>$ 4), while that of star-forming galaxies remains roughly constant ($n$ $\\approx$ 2.5). By decomposing galaxy profiles into bulge+disk components, we find that massive galaxies at high redshift have prominent stellar disks, which are also evident from visual inspection of the images. By $z$ $\\ap...

  15. Models of Late-Type Disk Galaxies: 1-D Versus 2-D

    CERN Document Server

    Mineikis, Tadas

    2015-01-01

    We investigate the effects of stochasticity on the observed galaxy parameters by comparing our stochastic star formation two-dimensional (2-D) galaxy evolution models with the commonly used one-dimensional (1-D) models with smooth star formation. The 2-D stochastic models predict high variability of the star formation rate and the surface photometric parameters across the galactic disks and in time.

  16. Star Formation in Isolated Disk Galaxies. I. Models and Star Formation Characteristics

    CERN Document Server

    Li, Y; Klessen, R S; Li, Yuexing; Low, Mordecai-Mark Mac; Klessen, Ralf S.

    2005-01-01

    We model star formation in a wide range of isolated disk galaxies composed of a dark matter halo and a disk of stars and isothermal gas, using a three-dimensional smoothed particle hydrodynamics code. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. They reach masses characteristic of stellar clusters. In this paper, we describe our galaxy models and numerical methods, followed by an investigation of the gravitational instability in these galaxies. Gravitational collapse forms star clusters with correlated positions and ages, as observed in the Large Magellanic Cloud. Gravitational instability alone acting in unperturbed galaxies appears sufficient to produce flocculent spiral arms, though not more organized patterns. Unstable galaxies show collapse in thin layers in the galactic plane; associated dust will form thin dust lanes in those galaxies, in agreement with observations. We find an exponential relationship between the global star formation timescale and ...

  17. Our Milky Way as a Pure-Disk Galaxy -- A Challenge for Galaxy Formation

    CERN Document Server

    Shen, Juntai; Kormendy, John; Howard, Christian D; De Propris, Roberto; Kunder, Andrea

    2010-01-01

    Bulges are commonly believed to form in the dynamical violence of galaxy collisions and mergers. Here we model the stellar kinematics of the Bulge Radial Velocity Assay (BRAVA), and find no sign that the Milky Way contains a classical bulge formed by scrambling pre-existing disks of stars in major mergers. Rather, the bulge appears to be a bar, seen somewhat end-on, as hinted from its asymmetric boxy shape. We construct a simple but realistic N-body model of the Galaxy that self-consistently develops a bar. The bar immediately buckles and thickens in the vertical direction. As seen from the Sun, the result resembles the boxy bulge of our Galaxy. The model fits the BRAVA stellar kinematic data covering the whole bulge strikingly well with no need for a merger-made classical bulge. The bar in our best fit model has a half-length of ~ 4kpc and extends 20 degrees from the Sun-Galactic Center line. We use the new kinematic constraints to show that any classical bulge contribution cannot be larger than ~ 8% of the ...

  18. Formation of ultra-compact blue dwarf galaxies and their evolution into nucleated dwarfs

    CERN Document Server

    Bekki, Kenji

    2015-01-01

    We propose that there is an evolutionary link between ultra-compact blue dwarf galaxies (UCBDs) with active star formation and nucleated dwarfs based on the results of numerical simulations of dwarf-dwarf merging. We consider the observational fact that low-mass dwarfs can be very gas-rich, and thereby investigate the dynamical and chemical evolution of very gas-rich, dissipative dwarf-dwarf mergers. We find that the remnants of dwarf-dwarf mergers can be dominated by new stellar populations formed from the triggered starbursts and consequently can have blue colors and higher metallicities (Z~[0.2-1]Z_sun). We also find that the remnants of these mergers can have rather high mass-densities (10^4 M_sun pc^-3) within the central 10 pc and small half-light radii (40-100 pc). The radial stellar structures of some merger remnants are similar to those of nucleated dwarfs. Star formation can continue in nuclear gas disks (R<100 pc) surrounding stellar galactic nuclei (SGNs) so that the SGNs can finally have multi...

  19. Deep multiband surface photometry on star forming galaxies: I. A sample of 24 blue compact galaxies

    CERN Document Server

    Micheva, Genoveva; Bergvall, Nils; Zackrisson, Erik; Masegosa, Josefa; Marquez, Isabel; Marquart, Thomas; Durret, Florence

    2012-01-01

    [Abridged] We present deep optical and near-infrared UBVRIHKs imaging data for 24 blue compact galaxies (BCGs). The sample contains luminous dwarf and intermediate-mass BCGs which are predominantly metal-poor, although a few have near-solar metallicities. We have analyzed isophotal and elliptical integration surface brightness and color profiles, extremely deep (mu_B<29 mag arcsec^{-2}) contour maps and RGB images for each galaxy in the sample. The colors are compared to different spectral evolutionary models. We detect extremely extended low surface brightness (LSB) components dominant beyond the Holmberg radius as well as optical bridges between companion galaxies at the mu_V~28th mag arcsec^{-2} isophotal level. The central surface brightness mu_0 and scale length h_r are derived from two radial ranges typically assumed to be dominated by the underlying host galaxy. We find that mu_0 and h_r of the BCGs host deviate from those of dwarf ellipticals (dE) and dwarf irregulars (dI) solely due to a strong bu...

  20. Disk Thicknesses and Some Parameters of 108 Non-Edge-On Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We present disk thicknesses, some other parameters and their statistics of 108 non-edge-on spiral galaxies. The method for determining the disk thickness is based on solving Poisson's equation for a disturbance of matter density in three-dimensional spiral galaxies.From the spiral arms found we could obtain the pitch angles, the inclination of the galactic disk, and the position of the innermost point (the forbidden region with radius r0 to the galactic center) of the spiral arm, and finally the thickness.

  1. The role of interactions in triggering bars, spiral arms and AGN in disk galaxies

    Science.gov (United States)

    Nair, Preethi; Ellison, Sara L.; Patton, David R.

    2016-01-01

    The role of secular structures like bars, rings and spiral arms in triggering star formation and AGN activity in disk galaxies are not well understood. In addition, the mechanisms which create and destroy these structures are not well characterized. Mergers are considered to be one of the main mechanisms which can trigger bars in massive disk galaxies. Using a sample of ~8000 close pair galaxies at 0.02 MaNGA will help to place stronger constraints on the role of these structures in triggering star formation and AGN.

  2. High-Redshift Galaxy Kinematics: Constraints on Models of Disk Formation

    CERN Document Server

    Robertson, Brant E

    2008-01-01

    Integral field spectroscopy of galaxies at redshift z~2 has revealed a population of early-forming, rotationally-supported disks. These high-redshift systems provide a potentially important clue to the formation processes that build disk galaxies in the universe. A particularly well-studied example is the z=2.38 galaxy BzK-15504, which was shown by Genzel et al. (2006) to be a rotationally supported disk despite the fact that its high star formation rate and short gas consumption timescale require a very rapid acquisition of mass. Previous kinematical analyses have suggested that z~2 disk galaxies like BzK-15504 did not form through mergers because their line-of-sight velocity fields display low levels of asymmetry. We perform the same kinematical analysis on a set of simulated disk galaxies formed in gas-rich mergers of the type that may be common at high redshift, and show that the remnant disks display low velocity field asymmetry and satisfy the criteria that have been used to classify high-redshift galax...

  3. Survival of pure disk galaxies over the last 8 billion years

    CERN Document Server

    Sachdeva, Sonali

    2016-01-01

    Pure disk galaxies without any bulge component, i.e., neither classical nor pseudo, seem to have escaped the affects of merger activity inherent to hierarchical galaxy formation models as well as strong internal secular evolution. We discover that a significant fraction (15 - 18 %) of disk galaxies in the Hubble Deep Field (0.4 < z < 1.0) as well as in the local Universe (0.02 < z < 0.05) are such pure disk systems (hereafter, PDS). The spatial distribution of light in these PDS is well described by a single exponential function from the outskirts to the centre and appears to have remained intact over the last 8 billion years keeping the mean central surface brightness and scale-length nearly constant. These two disk parameters of PDS are brighter and shorter, respectively, than of those disks which are part of disk galaxies with bulges. Since the fraction of PDS as well as their profile defining parameters do not change, it indicates that these galaxies have not witnessed either major mergers or ...

  4. Star Formation in Isolated Disk Galaxies. II. Schmidt Laws and Star Formation Efficiency

    CERN Document Server

    Li, Y; Klessen, R S; Li, Yuexing; Low, Mordecai-Mark Mac

    2005-01-01

    We model star formation in a wide range of isolated disk galaxies, using a three-dimensional, smoothed particle hydrodynamics code. The model galaxies include a dark matter halo and a disk of stars and isothermal gas. Absorbing sink particles are used to directly measure the mass of gravitationally collapsing gas. Below the density at which they are inserted, the collapsing gas is fully resolved. The star formation rate measured in our models declines exponentially with time. Radial profiles of atomic and molecular gas and star formation rate reproduce observed behavior. We derive from our models and discuss both the global and local Schmidt laws for star formation: power-law relations between surface densities of gas and star formation rate. The global Schmidt law observed in disk galaxies is quantitatively reproduced by our models. We find that the surface density of star formation rate directly correlates with the strength of local gravitational instability. The local Schmidt laws of individual galaxies in...

  5. EXTREME GAS FRACTIONS IN CLUMPY, TURBULENT DISK GALAXIES AT z ∼ 0.1

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, David B.; Glazebrook, Karl; Bassett, Robert [Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC 3122 (Australia); Bolatto, Alberto [Laboratory of Millimeter Astronomy, University of Maryland, College Park, MD 29742 (United States); Obreschkow, Danail [ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), 44 Rosehill Street, Redfern, NSW 2016 (Australia); Cooper, Erin Mentuch [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Wisnioski, Emily [Max Planck Institute for Extraterrestrial Physics, D-85741 Garching (Germany); Abraham, Roberto G. [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H8 (Canada); Damjanov, Ivana [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Green, Andy [Australian Astronomical Observatory, P.O. Box 970, North Ryde, NSW 1670 (Australia); McGregor, Peter, E-mail: dfisher@swin.edu.au [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston, ACT 2611 (Australia)

    2014-08-01

    In this Letter, we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby universe (z ∼ 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted Hα reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20%-30% and depletion times of t {sub dep} ∼ 0.5 Gyr (assuming a Milky-Way-like α{sub CO}). These properties are unlike those expected for low-redshift galaxies of comparable specific star formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies break the degeneracy between gas fraction and redshift, and we show that the depletion time per specific star formation rate for galaxies is closely tied to gas fraction, independent of redshift. We also show that the gas dynamics of two of our local targets corresponds to those expected from unstable disks, again resembling the dynamics of high-z disks. These results provide evidence that DYNAMO galaxies are local analogs to the clumpy, turbulent disks, which are often found at high redshift.

  6. Noncircular Outer Disks in Unbarred S0 Galaxies: NGC 502 and NGC 5485

    CERN Document Server

    Sil'chenko, Olga K

    2016-01-01

    Strongly noncircular outer stellar disks have been found in two unbarred SA0 galaxies by analyzing spectroscopic data on the rotation of stars and photometric data on the shape and orientation of the isophotes. In NGC 502, the oval distortion of the disk is manifested as two elliptical rings, the inner and the outer ones, covering wide radial zones between the bulge and the disk and at the outer edge of the stellar disk. Such a structure may be a consequence of the so-called "dry" minor merger - multiple accretion of gas-free satellites. In NGC 5485, the kinematical major axis does not coincide with the orientation of isophotes in the disk-dominated region, and for this galaxy the conclusion about its global triaxial structure is unavoidable.

  7. Studies of the association of faint blue and luminous galaxies using the Hitchhiker parallel camera

    CERN Document Server

    Jones, J B; Phillipps, S; Davies, J I; Morgan, I; Disney, M J

    1996-01-01

    At B magnitudes >~ 24 there is a well-known excess of galaxies (compared to standard models) which is probably due to an (evolving) population of sub-L* galaxies at moderate redshifts (<~ 0.4). One particular hypothesis which is hard to test directly via number counts or even redshift surveys is the possibility that the faint blue galaxies are in fact sub-galactic objects destined to merge by the present day to form current giant galaxies. If this were the case we might expect to find the faint blue galaxies in the vicinity of ~ L* galaxies (at redshifts =~ 0.2 to 0.4) with which they can merge (the blue galaxies are already known to be weakly clustered among themselves, limiting the possibility for multiple mergers of small fragments). In this paper we look for evidence of such clustering of faint blue galaxies around larger systems using candidates chosen photometrically from deep multicolour CCD images using the Hitchhiker parallel camera. A sample of candidate L^\\ast galaxies expected to lie at redshif...

  8. Outer Spiral Disks as Clues to Galaxy Formation and Evolution

    CERN Document Server

    Vlajić, Marija

    2010-01-01

    Recent studies of outer spiral disks have given rise to an abundance of new results. We discuss the observational and theoretical advances that have spurred the interest in disk outskirts, as well as where we currently stand in terms of our understanding of outer disk structure, ages and metallicities.

  9. Disk mass and disk heating in the spiral galaxy NGC 3223

    CERN Document Server

    Gentile, G; Baes, M; De Geyter, G; Koleva, M; Angus, G W; de Blok, W J G; Saftly, W; Viaene, S

    2015-01-01

    We present the stellar and gaseous kinematics of an Sb galaxy, NGC 3223, with the aim of determining the vertical and radial stellar velocity dispersion as a function of radius, which can help to constrain disk heating theories. Together with the observed NIR photometry, the vertical velocity dispersion is also used to determine the stellar mass-to-light (M/L) ratio, typically one of the largest uncertainties when deriving the dark matter distribution from the observed rotation curve. We find a vertical-to-radial velocity dispersion ratio of sigma_z/sigma_R=1.21+-0.14, significantly higher than expectations from known correlations, and a weakly-constrained Ks-band stellar M/L ratio in the range 0.5-1.7, at the high end of (but consistent with) the predictions of stellar population synthesis models. Such a weak constraint on the stellar M/L ratio, however, does not allow us to securely determine the dark matter density distribution. To achieve this, either a statistical approach or additional data (e.g. integr...

  10. Can Massive Dark Haloes Destroy the Disks of Dwarf Galaxies?

    CERN Document Server

    Fuchs, B

    2007-01-01

    Recent high-resolution simulations together with theoretical studies of the dynamical evolution of galactic disks have shown that contrary to wide-held beliefs a `live', dynamically responsive, dark halo surrounding a disk does not stabilize the disk against dynamical instabilities. We generalize Toomre's Q stability parameter for a disk-halo system and show that if a disk, which would be otherwise stable, is embedded in a halo, which is too massive and cold, the combined disk-halo system can become locally Jeans unstable. The good news is, on the other hand, that this will not happen in real dark haloes, which are in radial hydrostatic equilibrium. Even very low-mass disks are not prone to such dynamical instabilities.

  11. Clumpy Disks as a Testbed for Feedback-regulated Galaxy Formation

    Science.gov (United States)

    Mayer, Lucio; Tamburello, Valentina; Lupi, Alessandro; Keller, Ben; Wadsley, James; Madau, Piero

    2016-10-01

    We study the dependence of fragmentation in massive gas-rich galaxy disks at z > 1 on stellar feedback schemes and hydrodynamical solvers, employing the GASOLINE2 SPH code and the lagrangian mesh-less code GIZMO in finite mass mode. Non-cosmological galaxy disk runs with the standard delayed-cooling blastwave feedback are compared with runs adopting a new superbubble feedback, which produces winds by modeling the detailed physics of supernova-driven bubbles and leads to efficient self-regulation of star formation. We find that, with blastwave feedback, massive star-forming clumps form in comparable number and with very similar masses in GASOLINE2 and GIZMO. Typical clump masses are in the range 107-108 M ⊙, lower than in most previous works, while giant clumps with masses above 109 M ⊙ are exceedingly rare. By contrast, superbubble feedback does not produce massive star-forming bound clumps as galaxies never undergo a phase of violent disk instability. In this scheme, only sporadic, unbound star-forming overdensities lasting a few tens of Myr can arise, triggered by non-linear perturbations from massive satellite companions. We conclude that there is severe tension between explaining massive star-forming clumps observed at z > 1 primarily as the result of disk fragmentation driven by gravitational instability and the prevailing view of feedback-regulated galaxy formation. The link between disk stability and star formation efficiency should thus be regarded as a key testing ground for galaxy formation theory.

  12. High star formation rates as the origin of turbulence in early and modern disk galaxies.

    Science.gov (United States)

    Green, Andrew W; Glazebrook, Karl; McGregor, Peter J; Abraham, Roberto G; Poole, Gregory B; Damjanov, Ivana; McCarthy, Patrick J; Colless, Matthew; Sharp, Robert G

    2010-10-07

    Observations of star formation and kinematics in early galaxies at high spatial and spectral resolution have shown that two-thirds are massive rotating disk galaxies, with the remainder being less massive non-rotating objects. The line-of-sight-averaged velocity dispersions are typically five times higher than in today's disk galaxies. This suggests that gravitationally unstable, gas-rich disks in the early Universe are fuelled by cold, dense accreting gas flowing along cosmic filaments and penetrating hot galactic gas halos. These accreting flows, however, have not been observed, and cosmic accretion cannot power the observed level of turbulence. Here we report observations of a sample of rare, high-velocity-dispersion disk galaxies in the nearby Universe where cold accretion is unlikely to drive their high star formation rates. We find that their velocity dispersions are correlated with their star formation rates, but not their masses or gas fractions, which suggests that star formation is the energetic driver of galaxy disk turbulence at all cosmic epochs.

  13. FUSE observations of the Blue Compact Dwarf Galaxy Mrk 59

    CERN Document Server

    Thuan, T X; Izotov, Yu I

    2001-01-01

    New FUSE far-UV spectroscopy of the nearby metal-deficient (Zsun/8) cometary Blue Compact Dwarf (BCD) galaxy Markarian (Mrk) 59 is discussed. The data are used to investigate element abundances in its interstellar medium. The H I absorption lines are characterized by narrow cores which are interstellar in origin and by broad wings which are stellar in origin. The mean interstellar H I column density is ~ 7x10E20 cm-2 in Mrk 59. No H2 lines are seen and N(H2) is < 10E15 cm-2 at the 10 sigma level. The lack of diffuse H2 is due to the combined effect of a strong UV radiation field which destroys the H2 molecules and a low metallicity which leads to a scarcity of dust grains necessary for H2 formation. P-Cygni profiles of the S VI 933.4, 944.5 A and O VI 1031.9, 1037.6 A lines are seen, indicating the presence of very hot O stars and a stellar wind terminal velocity of ~ 1000 km/s. By fitting the line profiles with multiple components having each a velocity dispersion b = 7 km/s and spanning a radial velocity...

  14. The DiskMass Survey. X. Radio synthesis imaging of spiral galaxies

    CERN Document Server

    Martinsson, Thomas P K; Bershady, Matthew A; Westfall, Kyle B; Andersen, David R; Swaters, Rob A

    2016-01-01

    We present results from 21 cm radio synthesis imaging of 28 spiral galaxies from the DiskMass Survey obtained with the VLA, WSRT, and GMRT facilities. We detail the observations and data reduction procedures and present a brief analysis of the radio data. We construct 21 cm continuum images, global HI emission-line profiles, column-density maps, velocity fields, and position-velocity diagrams. From these we determine star formation rates (SFRs), HI line widths, total HI masses, rotation curves, and azimuthally-averaged radial HI column-density profiles. All galaxies have an HI disk that extends beyond the readily observable stellar disk, with an average ratio and scatter of R_{HI}/R_{25}=1.35+/-0.22, and a majority of the galaxies appear to have a warped HI disk. A tight correlation exists between total HI mass and HI diameter, with the largest disks having a slightly lower average column density. Galaxies with relatively large HI disks tend to exhibit an enhanced stellar velocity dispersion at larger radii, ...

  15. Galaxy And Mass Assembly: Deconstructing Bimodality - I. Red ones and blue ones

    CERN Document Server

    Taylor, Edward N; Baldry, Ivan K; Bland-Hawthorn, Joss; Brown, Michael J I; Colless, Matthew; Driver, Simon; Norberg, Peder; Robotham, Aaron S G; Alpaslan, Mehmet; Brough, Sarah; Cluver, Michelle E; Gunawhardhana, Madusha; Kelvin, Lee S; Liske, Jochen; Conselice, Christopher J; Croom, Scott; Foster, Caroline; Jarrett, Thomas H; Lopez, Maritza Lara; Loveday, Jon

    2014-01-01

    We measure the mass functions for generically red and blue galaxies, using a z 8.7 field galaxies from the Galaxy And Mass Assembly (GAMA) survey. Our motivation is that, as we show, the dominant uncertainty in existing measurements stems from how 'red' and 'blue' galaxies have been selected/defined. Accordingly, we model our data as two naturally overlapping populations, each with their own mass function and colour-mass relation, which enables us characterise the two populations without having to specify a priori which galaxies are 'red' and 'blue'. Our results then provide the means to derive objective operational definitions for the terms 'red' and 'blue', which are based on the phenomenology of the colour-mass diagrams. Informed by this descriptive modelling, we show that: 1.) after accounting for dust, the stellar colours of 'blue' galaxies do not depend strongly on mass; 2.) the tight, flat 'dead sequence' does not extend much below log M* ~ 10.5; instead, 3.) the stellar colours of 'red' galaxies vary...

  16. The Majority of Compact Massive Galaxies at z~2 are Disk Dominated

    CERN Document Server

    van der Wel, Arjen; Wuyts, Stijn; McGrath, Elizabeth J; Koekemoer, Anton M; Bell, Eric F; Holden, Bradford P; Robaina, Aday R; McIntosh, Daniel H

    2011-01-01

    We investigate the stellar structure of massive, quiescent galaxies at z~2, based on HST/WFC3 imaging from the Early Release Science program. Our sample of 14 galaxies has stellar masses of M* > 10^{10.8} Msol and photometric redshifts of 1.5 < z < 2.5. In agreement with previous work, their half-light radii are <2 kpc, much smaller than equally massive galaxies in the present-day universe. A significant subset of the sample appear highly flattened in projection, which implies, considering viewing angle statistics, that a significant fraction of the galaxies in our sample have pronounced disks. This is corroborated by two-dimensional surface brightness profile fits. We estimate that 65% +/- 15% of the population of massive, quiescent z~2 galaxies are disk-dominated. The median disk scale length is 1.5 kpc, substantially smaller than the disks of equally massive galaxies in the present-day universe. Our results provide strong observational evidence that the much-discussed ultra-dense high-redshift gal...

  17. Photographic photometry of 16000 galaxies on ESO blue and red survey plates

    NARCIS (Netherlands)

    Lauberts, A.; Valentijn, E. A.

    1985-01-01

    An ongoing photometric survey of 16,000 galaxies on ESO red and blue plates is described. The galaxies of the ESO/Uppsala Catalog (Lauberts, 1982) are being PDS scanned, and the results are combined with existing photometry and supplementary observational data obtained at the 1-m ESO telescope to fo

  18. The power spectra of non-circular motions in disk galaxies

    Science.gov (United States)

    Westfall, Kyle; Laws, Anna S. E.; MaNGA Team

    2016-01-01

    Using data from the first year of the SDSS-IV/MaNGA survey, we present a preliminary study of the amplitude of non-circular motions in a sample of disk galaxies. We select galaxies that have either a visual classification as a spiral galaxy by the Galaxy Zoo project (Lintott et al. 2011) and/or a measured Sersic index of less than 2.5 from the NASA-Sloan Atlas (nsatlas.org). We also remove high-inclination systems by selecting galaxies with isophotal ellipticity measurements of less than 0.6, implying an inclination of less than 65 degrees. For each galaxy, we fit a tilted-disk model to the observed line-of-sight velocities (Andersen & Bershady 2013). The geometric projection of the circularly rotating disk is simultaneously fit to both the ionized-gas (H-alpha) and stellar kinematics, whereas the rotation curves of the two dynamical tracers are allowed to be independent. We deproject the residuals of the velocity-field fit to the disk-plane polar coordinates and select a radial region that is fully covered in aziumuth, yet not undersampled by the on-sky spaxel. Similar to the approach taken by Bovy et al. (2015) for the Milky Way, we then compute the two-dimensional power spectrum of this velocity-residual map, which provides the amplitude of non-circular motions at all modes probed by the data. Our preliminary analysis reveals disk-plane non-circular motions in both the stars and ionized-gas with typical peak amplitudes of approximately 20 km/s. Additionally, our initial findings appear to demonstrate that non-circular motions in barred galaxies are stronger in the ionized gas than in the stars, a trend not seen in unbarred galaxies.

  19. Are Globular Clusters the Remnant Nuclei of Progenitor Disk Galaxies?

    CERN Document Server

    Boeker, Torsten

    2007-01-01

    The globular cluster system of a typical spheroidal galaxy makes up about 0.25% of the total galaxy mass (McLaughlin 1999). This is roughly the same mass fraction as contained in the nuclear star clus- ter (or stellar nucleus) present in most nearby low-mass galaxies. Motivated by this "coincidence", this Letter discusses a scenario in which globular clusters of present-day galaxies are the surviving nuclei of the dwarf galaxies that - according to the hierarchical merging paradigm of galaxy forma- tion - constitute the "building blocks" of present-day massive galaxies. This scenario, which was first suggested by Freeman (1993), has become more attractive recently in the light of studies that demonstrate a complex star formation history in a number of massive globular clusters.

  20. Baryonic inflow and outflow histories in disk galaxies as revealed from observations of distant star-forming galaxies

    Science.gov (United States)

    Toyouchi, Daisuke; Chiba, Masashi

    2016-08-01

    Gas inflow and outflow are the most important processes, which determine the structural and chemical evolution of a disk galaxy like the Milky Way. In order to get new insights into these baryonic processes in Milky Way like galaxies (MWLGs), we consider the data of distant star-forming galaxies and investigate the evolution of the radial density profile of their stellar components and the associated total amount of gaseous inflow and outflow. For this purpose, we analyze the redshift evolution of their stellar mass distribution, combined with the scaling relations between the mass of baryonic components, star formation rate and chemical abundance for both high- and low-z star-forming galaxies. As a result, we find the new relations between star formation rate and inflow/outflow rate as deduced from these distant galaxies, which will provide fundamental information for understanding the structural and chemical evolution of MWLGs.

  1. The imprint of radial migration on the vertical structure of galaxy disks

    CERN Document Server

    Vera-Ciro, Carlos; Navarro, Julio F

    2016-01-01

    We use numerical simulations to examine the effects of radial migration on the vertical structure of galaxy disks. The simulations follow three exponential disks of different mass but similar circular velocity, radial scalelength, and (constant) scale height. The disks develop different non-axisymmetric patterns, ranging from feeble, long-lived multiple arms to strong, rapidly-evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk particles, mixing the disk radially and blurring pre-existing gradients. Migration affects primarily stars with small vertical excursions, regardless of spiral pattern. This "provenance bias" largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, ...

  2. Structure, dynamics and evolution of disk galaxies in a hierarchical formation scenario

    CERN Document Server

    Firmani, C

    1999-01-01

    Using galaxy evolutionary models in a hierarchical formation scenario, we predict the structure, dynamics and evolution of disk galaxies in a LCDM universe. Our models include star formation and hydrodynamics of the ISM. We find that the Tully-Fisher relation (TFR) in the I and H bands is an imprint of the mass-velocity relation of the cosmological dark halos. The scatter of the TFR originates mainly from the scatter in the dark halo structure and, to a minor extension, from the dispersion of the primordial spin parameter lambda. Our models allow us to explain why low and high surface brightness galaxies have the same TFR. The disk gas fractions predicted agree with the observations. The disks formed within the growing halos have nearly exponential surface brightness and flat rotation curves. Towards high redshifts, the zero-point of the TFR in the H band increases while in the B-band it slightly decreases.

  3. Simulating disk galaxies and interactions in Milgromian dynamics

    CERN Document Server

    Thies, Ingo; Famaey, Benoit

    2016-01-01

    Since its publication 1983, Milgromian dynamics (aka MOND) has been very successful in modeling the gravitational potential of galaxies from baryonic matter alone. However, the dynamical modeling has long been an unsolved issue. In particular, the setup of a stable galaxy for Milgromian N-body calculations has been a major challenge. Here, I will show a way to set up disc galaxies in MOND for calculations in the PHANTOM OF RAMSES (PoR) code by L\\"ughausen (2015) and Teyssier (2002). The method is done by solving the QUMOND Poisson equations based on a baryonic and a phantom dark matter component. The resulting galaxy models are stable after a brief settling period for a large mass and size range. Simulations of single galaxies as well as colliding galaxies are shown.

  4. The Evolution of Stellar Populations in the Outer Disks of Spiral Galaxies

    CERN Document Server

    Alberts, Stacey; Dong, Hui; Johnson, L C; Dale, Daniel A; Bianchi, Luciana; Chandar, Rupali; Kennicutt, Robert C; Meurer, Gerhardt R; Regan, Michael; Thilker, David

    2011-01-01

    We investigate recent star formation in the extended ultraviolet (XUV) disks of five nearby galaxies (NGC 0628, NGC 2090, NGC 2841, NGC 3621, and NGC 5055) using a long wavelength baseline comprised of ultraviolet and mid-infrared imaging from the Galaxy Evolution Explorer and the Spitzer Infrared Array Camera. We identify 229 unresolved stellar complexes across targeted portions of their XUV disks and utilize spectral energy distribution fitting to measure their stellar ages and masses through comparison with Starburst99 population synthesis models of instantaneous burst populations. We find that the median age of outer disk associations in our sample is ~100 Myr with a large dispersion that spans the entire range of our models (1 Myr-1 Gyr). This relatively evolved state for most associations addresses the observed dearth of Halpha emission in some outer disks, as Halpha can only be observed in star forming regions younger than ~10 Myr. The large age dispersion is robust against variations in extinction (in...

  5. A Blue Tilt in the Globular Cluster System of the Milky Way-like Galaxy NGC 5170

    CERN Document Server

    Forbes, Duncan; Harris, William; Bailin, Jeremy; Strader, Jay; Brodie, Jean; Larsen, Soeren

    2009-01-01

    Here we present HST/ACS imaging, in the B and I bands, of the edge-on Sb/Sc galaxy NGC 5170. Excluding the central disk region region, we detect a 142 objects with colours and sizes typical of globular clusters (GCs). Our main result is the discovery of a `blue tilt' (a mass-metallicity relation), at the 3sigma level, in the metal-poor GC subpopulation of this Milky Way like galaxy. The tilt is consistent with that seen in massive elliptical galaxies and with the self enrichment model of Bailin & Harris. For a linear mass-metallicity relation, the tilt has the form Z ~ L^{0.42 +/- 0.13}. We derive a total GC system population of 600 +/- 100, making it much richer than the Milky Way. However when this number is normalised by the host galaxy luminosity or stellar mass it is similar to that of M31. Finally, we report the presence of a potential Ultra Compact Dwarf of size ~ 6 pc and luminosity M_I ~ -12.5, assuming it is physically associated with NGC 5170.

  6. Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae

    Science.gov (United States)

    Herrero-Illana, R.; Pérez-Torres, M. Á.; Alberdi, A.

    2012-04-01

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ~100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M 82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.''1) radio observations published in the literature (for M 82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes ~100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of supernovae (SNe) in the nuclear starbursts of M 82, Arp 299-A, and Arp 220, and derived scale-length values for the putative nuclear disks powering the bursts in those central regions. The scale lengths for the (exponential) disks range from ~20-30 pc for Arp 299-A and Arp 220, up to ~140 pc for M 82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. Our results support scenarios where a nuclear disk of size ~100 pc is formed in (U)LIRGs, and sustained by gas pressure, in which case the accretion onto the black hole could be lowered by supernova feedback. Appendices are available in electronic form at http://www.aanda.org

  7. Downsizing among disk galaxies and the role of the environment

    CERN Document Server

    Gavazzi, Giuseppe

    2009-01-01

    The study of PopI and PopII indicators in galaxies has a profound impact on our understanding of galaxy evolution. Their present (z=0) ratio suggests that the star formation history of galaxies was primarily dictated by their global mass. Since 1989 Luis Carrasco and I spent most of our sleepless nights gathering H_alpha and near infrared surface photometry of galaxies in the local Universe and focused most of our scientific career on these two indicators trying to convince the community that the mass was the key parameter to their evolution. We were unsuccessful, until in 2004 the Sloan team rediscovered this phenomenon and named it "downsizing"

  8. The Difference between the α-disks of Seyfert 1 Galaxies and Quasars

    Institute of Scientific and Technical Information of China (English)

    Wei-Hao Bian; Hong Dong; Yong-Heng Zhao

    2004-01-01

    In a previous paper, it was suggested that contamination of the nuclear luminosity by the host galaxy plays an important role in determining the parameters of the standard α disk of AGNs. Using the nuclear absolute B band magnitude instead of the total absolute B band magnitude, we have recalculated the central black hole masses, accretion rates and disk inclinations for 20 Seyfert 1 galaxies and 17 Palomar-Green (PG) quasars. It is found that a small value of α is needed for the Seyfert 1 galaxies than for the PG quasars. This difference in α possibly leads to the different properties of Seyfert 1 galaxies and quasars. Furthermore, we find most of the objects in this sample are not accreting at super-Eddington rates if we adopt the nuclear optical luminosity in our calculation.

  9. The Star Formation Histories of Disk and E/S0 Galaxies from Resolved Stars

    CERN Document Server

    Olsen, Knut A G; Saha, Abhijit; Skillman, Evan; Williams, Benjamin F; Wyse, Rosemary F G

    2009-01-01

    The resolved stellar populations of local galaxies, from which it is possible to derive complete star formation and chemical enrichment histories, provide an important way to study galaxy formation and evolution that is complementary to lookback time studies. We propose to use photometry of resolved stars to measure the star formation histories in a statistical sample of galaxy disks and E/S0 galaxies near their effective radii. These measurements would yield strong evidence to support critical questions regarding the formation of galactic disks and spheroids. The main technological limitation is spatial resolution for photometry in heavily crowded fields, for which we need improvement by a factor of ~10 over what is possible today with filled aperture telescopes.

  10. A new study on the thick disk population component of the Galaxy

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The newly-raised problem as to whether our Galaxy may contain a thick disk population component has aroused great interest. But up until now no conclusion has been reached unanimously for lack of observed data. Here this problem is discussed based on seven Basel field data calibrated recently and strong evidence is provided. New results on the values of structural parameters, luminosity functions and metal structure of the thick disk are also presented.

  11. A Citizen-Science-enabled Comprehensive Search for XUV-disk Galaxies

    Science.gov (United States)

    Thilker, David A.

    2017-03-01

    Initial efforts to identify extended UV disk (XUV-disk) galaxies were confined to nearby targets using image products from early in the GALEX mission. We developed a beta Zooniverse-based citizen science project to address this issue, specifically (1) allowing a dramatically larger galaxy sample by crowd-sourcing blink comparison UV-optical image inspection to volunteers, and (2) incorporating all archived GALEX data for each target considered. We aim to widely deploy this project to the public within the upcoming year.

  12. LoCuSS: Exploring the selection of faint blue background galaxies for cluster weak-lensing

    Science.gov (United States)

    Ziparo, Felicia; Smith, Graham P.; Okabe, Nobuhiro; Haines, Chris P.; Pereira, Maria J.; Egami, Eiichi

    2016-10-01

    Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogues derived from the COSMOS survey and our own observations of massive galaxy clusters at z ≃ 0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to safely identify faint blue background galaxies with the same 1 per cent contamination level that we have achieved with red galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. Nevertheless, our least contaminated blue galaxy sample yields stacked weak-lensing results consistent with our previously published results based on red galaxies, and we show that the stacked clustercentric number density profile of these faint blue galaxies is consistent with expectations from consideration of the lens magnification signal of the clusters. Indeed, the observed number density of blue background galaxies changes by ˜10 - 30 per cent across the radial range over which other surveys assume it to be flat.

  13. Evolutionary models for disk galaxies, a comparison with the observations up to intermediate redshifts (z<~1)

    CERN Document Server

    Firmani, C

    1998-01-01

    We present a scenario for the formation and evolution of disk galaxies within the framework of an inflationary CDM universe, and we compare the results with observations ranking from the present-day up to z~1. Galactic disks are built-up inside-out by gas infall with accretion rates driven by the cosmological mass aggregation history (MAH). We generate the MAHs for a Gaussian density fluctuation field, and we calculate the gravitational collapse and virialization of the dark halos. Assuming detailed angular momentum conservation, disks in centrifugal equilibrium are built-up within them. The disk galactic evolution is followed through a physically self-consistent approach. The main disk galaxy properties and their correlations are determined by the mass, the MAH, and the spin parameter. The models give exponential disk surface brightness (SB) profiles with realistic parameters (including LSB galaxies), nearly flat rotation curves, and negative gradients in the B-V radial profile. The main trends across the Hu...

  14. Dark matter distribution and its impact on the evolution of galaxy disks

    CERN Document Server

    Combes, F

    2012-01-01

    The role of dark matter halos in galaxy disk evolution is reviewed, in particular the stabilisation of disks through self-gravity reduction, or the bar development through angular momentum exchange. Triaxial dark halos tend to weaken bars. When the dark mass inside the bar region is negligible, the bar develops through angular momentum exchange between inner and outer disk, and between stars and gas. Self-regulating cycles on the bar strength may develop in the presence of external gas accretion. Dynamical friction on dark halos slows down bars, which puts constraints on the dark matter amount inside the inner disk. During galaxy formation, baryons can lose most of their angular momentum if the infall is misaligned with the dark matter axes. Stable disks can form aligned with the minor axis of the dark halo. A sudden change in the infall direction, otherwise steady, can produce the peculiar polar ring galaxies. The dark matter halo can then be aligned along the polar disk. Misaligned infall can also maintain ...

  15. Near-infrared observations of galaxies in Pisces-Perseus; 2, Extinction effects and disk opacity

    CERN Document Server

    Moriondo, G; Haynes, M P

    1998-01-01

    We study the correlations with inclination of H-band disk and bulge structural parameters and I-H colour profiles for a sample of 154 spiral galaxies, in order to detect possible effects due to internal extinction by dust. The selection of the sample assures that galaxies at different inclinations are not intrinsically different, so that the observed correlations represent the real behaviour of the parameter considered. All the parameters are derived from a bi-dimensional fitting of the galaxy image. We find that extinction, though small at near infrared wavelengths, is sufficient to produce observable effects. In particular the observed increase of the average disk scalelength and the reddening of the disk I-H colour at high inclinations are clear signatures of the presence of dust. The total H-band disk luminosity depends little on inclination; on the other hand significant corrections to the face-on aspect are derived for the H-band central disk brightness and the disk scalelength. The bulge parameters exh...

  16. Bulges versus disks: the evolution of angular momentum in cosmological simulations of galaxy formation

    CERN Document Server

    Zavala, J; Frenk, Carlos S

    2007-01-01

    We investigate the evolution of angular momentum in simulations of galaxy formation in a cold dark matter universe. We analyse two model galaxies produced in the N-body/hydrodynamic simulations of Okamoto et al. Starting from identical initial conditions, but using different assumptions for the baryonic physics, one of the simulations produced a bulge-dominated galaxy and the other one a disk-dominated galaxy. The main difference is the treatment of star formation and feedback, both of which were designed to be more efficient in the disk-dominated object. We find that the specific angular momentum of the disk-dominated galaxy tracks the evolution of the angular momentum of the dark matter halo very closely: the angular momentum grows as predicted by linear theory until the epoch of maximum expansion and remains constant thereafter. By contrast, the evolution of the angular momentum of the bulge-dominated galaxy resembles that of the central, most bound halo material: it also grows at first according to linear...

  17. Extreme gas fractions in clumpy, turbulent disk galaxies at z~0.1

    CERN Document Server

    Fisher, David B; Bolatto, Alberto; Obreschkow, Danail; Mentuch-Cooper, Erin; Wisnioski, Emily; BAssett, Robert; Abraham, Roberto G; Damjanov, Ivana; Green, Andy; McGregor, Peter

    2014-01-01

    In this letter we report the discovery of CO fluxes, suggesting very high gas fractions in three disk galaxies seen in the nearby Universe (z ~ 0.1). These galaxies were investigated as part of the DYnamics of Newly Assembled Massive Objects (DYNAMO) survey. High-resolution Hubble Space Telescope imaging of these objects reveals the presence of large star forming clumps in the bodies of the galaxies, while spatially resolved spectroscopy of redshifted Halpha reveals the presence of high dispersion rotating disks. The internal dynamical state of these galaxies resembles that of disk systems seen at much higher redshifts (1 < z < 3). Using CO(1-0) observations made with the Plateau de Bure Interferometer, we find gas fractions of 20-30% and depletion times of tdep ~ 0.5 Gyr (assuming a Milky Way-like CO conversion factor). These properties are unlike those expected for low- redshift galaxies of comparable specific star formation rate, but they are normal for their high-z counterparts. DYNAMO galaxies brea...

  18. Clustered star formation as a natural explanation for the Halpha cut-off in disk galaxies.

    Science.gov (United States)

    Pflamm-Altenburg, Jan; Kroupa, Pavel

    2008-10-02

    The rate of star formation in a galaxy is often determined by the observation of emission in the Halpha line, which is related to the presence of short-lived massive stars. Disk galaxies show a strong cut-off in Halpha radiation at a certain galactocentric distance, which has led to the conclusion that star formation is suppressed in the outer regions of disk galaxies. This is seemingly in contradiction to recent observations in the ultraviolet which imply that disk galaxies have star formation beyond the Halpha cut-off, and that the star-formation-rate surface density is linearly related to the underlying gas surface density, which is a shallower relationship than that derived from Halpha luminosities. In a galaxy-wide formulation, the clustered nature of star formation has recently led to the insight that the total galactic Halpha luminosity is nonlinearly related to the galaxy-wide star formation rate. Here we show that a local formulation of the concept of clustered star formation naturally leads to a steeper radial decrease in the Halpha surface luminosity than in the star-formation-rate surface density, in quantitative agreement with the observations, and that the observed Halpha cut-off arises naturally.

  19. Large-Scale Outer Rings of Early-type Disk Galaxies

    CERN Document Server

    Kostiuk, Irina P

    2015-01-01

    We have searched for presence of current star formation in outer stellar rings of early-type disk (S0-Sb) galaxies by inspecting a representative sample of nearby galaxies with rings from the recent Spitzer catalog ARRAKIS (Comeron et al. 2014). We have found that regular rings (of R-type) reveal young stellar population with the age of less than 200~Myr in about half of all the cases, while in the pseudorings (open rings, R'), which inhabit only spiral galaxies, current star formation proceeds almost always.

  20. Galaxy Zoo: the dependence of the star formation-stellar mass relation on spiral disk morphology

    CERN Document Server

    Willett, Kyle W; Simmons, Brooke D; Masters, Karen L; Skibba, Ramin A; Kaviraj, Sugata; Melvin, Thomas; Wong, O Ivy; Nichol, Robert C; Cheung, Edmond; Lintott, Chris J; Fortson, Lucy

    2015-01-01

    We measure the stellar mass-star formation rate relation in star-forming disk galaxies at z1. Of the galaxies lying significantly above the M-SFR relation in the local Universe, more than 50% are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.

  1. The dark matter halo shape of edge-on disk galaxies - I. HI observations

    CERN Document Server

    O'Brien, J C; van der Kruit, P C; Bosma, A

    2010-01-01

    This is the first paper of a series in which we will attempt to put constraints on the flattening of dark halos in disk galaxies. We observe for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. In this paper, we define a sample of 8 HI-rich late-type galaxies suitable for this purpose and present the HI observations.

  2. Ionized gas disks in Elliptical and S0 galaxies at $z<1$

    CERN Document Server

    Jaffe, Yara L; Ziegler, Bodo; Kuntschner, Harald; Zaritsky, Dennis; Rudnick, Gregory; Poggianti, Bianca M; Hoyos, Carlos; Halliday, Claire; Demarco, Ricardo

    2014-01-01

    We analyse the extended, ionized-gas emission of 24 early-type galaxies (ETGs) at $0galaxies have disturbed gas kinematics, while 14 have rotating gas disks. In addition, 15 galaxies are in the field, while 9 are in the infall regions of clusters. This implies that, if the gas has an internal origin, this is likely stripped as the galaxies get closer to the cluster centre. If the gas instead comes from an external source, then our results suggest that this is more likely acquired outside the cluster environment, where galaxy-galaxy interactions more commonly take place. We analyse the Tully-Fisher relation of the ETGs with gas disks, and compare them to EDisCS spirals. Taking a matched range of redshifts, $M_{B}<-20$, and excluding galaxies with large velocity uncertainties, we find that, at fixed rotational velocity, ETGs ar...

  3. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    Science.gov (United States)

    Greene, J. E.; Seth, A.; Kim, M.; Läsker, R.; Goulding, A.; Gao, F.; Braatz, J. A.; Henkel, C.; Condon, J.; Lo, K. Y.; Zhao, W.

    2016-08-01

    We use new precision measurements of black hole (BH) masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive BH mass. The megamaser-derived BH masses span 106-108 {M}⊙ , while all the galaxy properties that we examine (including total stellar mass, central mass density, and central velocity dispersion) lie within a narrower range. Thus, no galaxy property correlates tightly with {M}{BH} in ˜L* spiral galaxies as traced by megamaser disks. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed {σ }* the mean megamaser {M}{BH} are offset by -0.6 ± 0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not appear to show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to an inability to resolve their spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  4. Spectral decomposition of the stellar kinematics in the polar disk galaxy NGC 4650A

    CERN Document Server

    Coccato, L; Arnaboldi, M

    2014-01-01

    Context. The prototype of Polar Ring Galaxies NGC 4650A contains two main structural components, a central spheroid, which is the host galaxy, and an extended polar disk. Both photometric and kinematic studies revealed that these two components co-exist on two different planes within the central regions of the galaxy. Aims. The aim of this work is to study the spectroscopic and kinematic properties of the host galaxy and the polar disk in the central regions of NGC 4650A by disentangling their contributions to the observed galaxy spectrum. Methods. We applied the spectral decomposition technique introduced in previous works to long-slit spectroscopic observations in the CaII triplet region. We focused the analysis along the PA = 152 that corresponds to the photometric minor axis of the host galaxy, where the superimposition of the two components is more relevant and the spectral decomposition is necessary. We aim to disentangle the stars that move in the equatorial plane of the host galaxy from those that mov...

  5. DOWNSIZING AMONG DISK GALAXIES AND THE ROLE OF THE ENVIRONMENT

    Directory of Open Access Journals (Sweden)

    G. Gavazzi

    2009-01-01

    Full Text Available The study of PopI and PopII indicators in galaxies has a profound impact on our understanding of galaxy evolution. Their present (z = 0 ratio suggests that the star formation history of galaxies was primarily dictated by their global mass. Since 1989 Luis Carrasco and I spent most of our sleepless nights gathering H and near infrared surface photometry of galaxies in the local Universe and focused most of our scienti c career on these two indicators trying to convince the community that the mass was the key parameter to their evolution. We were unsuccessful, until in 2004 the Sloan team rediscovered this phenomenon and named it \\downsizing".

  6. The Star Formation Histories of Disk Galaxies: the Live, the Dead, and the Undead

    CERN Document Server

    Oemler, Augustus; Gladders, Michael D; Dressler, Alan; Poggianti, Bianca M; Vulcani, Benedetta

    2016-01-01

    We reexamine the systematic properties of local galaxy populations, using published surveys of star formation, structure, and gas content. After recalibrating star formation measures, we are able to reliably measure specific star formation rates well below the "main sequence" of star formation vs mass. We find an unexpectedly large population of galaxies with star formation rates intermediate between vigorously star-forming main sequence galaxies and passive galaxies, and with gas content disproportionately high for their star formation rates. Several lines of evidence suggest that these quiescent galaxies form a distinct population rather than a low star formation tail of the main sequence. We demonstrate that a tight main sequence, evolving with epoch, is a natural outcome of most histories of star formation and has little astrophysical significance, but that the quiescent population requires additional astrophysics to explain its properties. Using a simple model for disk evolution based on the observed dep...

  7. Clues to the Formation of Lenticular Galaxies Using Spectroscopic Bulge-Disk Decomposition

    CERN Document Server

    Johnston, Evelyn J; Merrifield, Michael R; Bedregal, Alejandro G

    2013-01-01

    Lenticular galaxies have long been thought of as evolved spirals, but the processes involved to quench the star formation are still unclear. By studying the individual star formation histories of the bulges and disks of lenticulars, it is possible to look for clues to the processes that triggered their transformation from spirals. To accomplish this feat, we present a new method for spectroscopic bulge-disk decomposition, in which a long-slit spectrum is decomposed into two one-dimensional spectra representing purely the bulge and disk light. We present preliminary results from applying this method to lenticular galaxies in the Virgo and Fornax Clusters, in which we show that the most recent star formation activity in these galaxies occurred within the bulges. We also find that the star formation timescales of the bulges are longer than the disks, and that more massive galaxies take longer to lose their gas during the transformation. These results point towards slow processes, such as ram-pressure stripping o...

  8. The growth of disks and bulges during hierarchical galaxy formation. I: fast evolution vs secular processes

    CERN Document Server

    Tonini, Chiara; Croton, Darren J; Wyithe, J Stuart B

    2016-01-01

    We present a theoretical model for the evolution of mass, angular momentum and size of galaxy disks and bulges, and we implement it into the semi-analytic galaxy formation code SAGE. The model follows both secular and violent evolutionary channels, including smooth accretion, disk instabilities, minor and major mergers. We find that the combination of our recipe with hierarchical clustering produces two distinct populations of bulges: merger-driven bulges, akin to classical bulges and ellipticals, and instability-driven bulges, akin to secular (or pseudo-)bulges. The model can successfully reproduce the mass-size relation of gaseous and stellar disks, the evolution of the mass-size relation of ellipticals, the Faber-Jackson relation, and the magnitude-colour diagram of classical and secular bulges. The model predicts only a small overlap of merger-driven and instability-driven components in the same galaxy, and predicts different bulge types as a function of galaxy mass and disk fraction. Bulge type also affe...

  9. HI study of the warped spiral galaxy NGC5055 : a disk/dark matter halo offset?

    NARCIS (Netherlands)

    Battaglia, G; Fraternali, F; Oosterloo, T; Sancisi, R

    2006-01-01

    We present a study of the Hi distribution and dynamics of the nearby spiral galaxy NGC 5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to 3.5 R-25, and shows a pronounced warp that starts at the end of the brigh

  10. HI study of the warped spiral galaxy NGC5055 : a disk/dark matter halo offset?

    NARCIS (Netherlands)

    Battaglia, G.; Fraternali, F.; Oosterloo, T.; Sancisi, R.

    2005-01-01

    Abstract: We present a study of the HI distribution and the dynamics of the nearby spiral galaxy NGC5055 based on observations with the Westerbork Synthesis Radio Telescope. The gaseous disk of NGC5055 extends out to about 40 kpc, equal to 3.5 R_25 and shows a pronounced warp, starting at the end of

  11. Near-Infrared Surface Photometry of Bulges and Disks of Spiral Galaxies : The Data

    NARCIS (Netherlands)

    Peletier, R. F.; Balcells, M.

    1997-01-01

    Abstract: We present optical and near-infrared (NIR) surface brightness and colour profiles,in bands ranging from U to K, for the disk and bulge components of a complete sample of 30 nearby S0 to Sbc galaxies with inclinations larger than 50 degrees. We describe in detail the observations and the de

  12. The Stars and Gas in Outer Parts of Galaxy Disks : Extended or Truncated, Flat or Warped?

    NARCIS (Netherlands)

    van der Kruit, P. C.; Funes, JG; Corsini, EM

    2008-01-01

    I review observations of truncations of stellar disks and models for their origin, compare observations of truncations in moderately inclined galaxies to those in edge-on systems and discuss the relation between truncations and H I-warps and their systematics and origin. Truncations are a common fea

  13. Radio continuum detection in blue early-type weak emission line galaxies

    CERN Document Server

    Paswan, A

    2016-01-01

    The star formation rates (SFRs) in weak emission line (WEL) galaxies in a volume-limited ($0.02 < z < 0.05$) sample of blue early-type galaxies (ETGs) identified from SDSS, are constrained here using 1.4 GHz radio continuum emission. The direct detection of 1.4 GHz radio continuum emission is made in 8 WEL galaxies and a median stacking is performed on 57 WEL galaxies using VLA FIRST images. The median stacked 1.4 GHz flux density and luminosity are estimated as 79 $\\pm$ 19 $\\mu$Jy and 0.20 $\\pm$ 0.05 $\\times$ 10$^{21}$ W Hz$^{-1}$ respectively. The radio far-infrared correlation in 4 WEL galaxies suggests that the radio continuum emission from WEL galaxies is most likely due to star formation activities. The median SFR for WEL galaxies is estimated as 0.23 $\\pm$ 0.06 M$_{\\odot}$yr$^{-1}$, which is much less compared to SFRs ($0.5 - 50$ M$_{\\odot}$yr$^{-1}$) in purely star forming blue ETGs. The SFRs in blue ETGs are found to be correlated with their stellar velocity dispersions ($\\sigma$) and decreasin...

  14. Spatially-resolved SFR in nearby disk galaxies using IFS data

    Science.gov (United States)

    Catalán-Torrecilla, C.; Gil de Paz, A.; Castillo-Morales, A.; Méndez-Abreu, J.; Pascual, S.; Ruiz-Lara, T.; de Lorenzo-Cáceres, A.; Sánchez-Menguiano, L.

    2017-03-01

    Exploring the spatial distribution of the star formation rate (SFR) in nearby galaxies is essential to understand their evolution through cosmic time. With this aim in mind, we use a representative sample that contains a variety of morphological types, the CALIFA Integral Field Spectroscopy (IFS) sample. Previous to this work, we have verified that our extinction-corrected Hα measurements successfully reproduce the values derived from other SFR tracers such as Hα obs + IR or UV obs + IR (Catalán-Torrecilla et al. 2015). Now, we go one step further applying 2-dimensional photometric decompositions (Méndez-Abreu et al. (2008), Méndez-Abreu et al. (2014)) over these datacubes. This method allows us to obtain the amount of SFR in the central part (bulge or nuclear source), the bar and the disk, separately. First, we determine the light coming from each component as the ratio between the luminosity in every component (bulge, bar or disk) and the total luminosity of the galaxy. Then, for each galaxy we multiply the IFS datacubes by these previous factors to recover the luminosity in each component. Finally, we derive the spectrum associated to each galaxy component integrating the spatial information in the weighted datacube using an elliptical aperture covering the whole galaxy. 2D photometric decomposition applied over 3D datacubes will give us a more detailed understanding of the role that disks play in more massive galaxies. Knowing if the disks in more massive SF galaxies have on average a lower or higher level of star formation activity and how these results are affected by the presence of nuclear bars are still open questions that we can now solve. We describe the behavior of these components in the SFR vs. stellar mass diagram. In particular, we highlight the role of the disks and their contribution to both the integrated SFR for the whole galaxy and the SFR in the disk at different stellar masses in the SFR vs. stellar mass diagram together with their

  15. A Spectroscopic Study of Blue Supergiant Stars in the Sculptor Galaxy NGC 55: Chemical Evolution and Distance

    Science.gov (United States)

    Kudritzki, R. P.; Castro, N.; Urbaneja, M. A.; Ho, I.-T.; Bresolin, F.; Gieren, W.; Pietrzyński, G.; Przybilla, N.

    2016-10-01

    Low-resolution (4.5-5 Å) spectra of 58 blue supergiant stars distributed over the disk of the Magellanic spiral galaxy NGC 55 in the Sculptor group are analyzed by means of non-LTE techniques to determine stellar temperatures, gravities, and metallicities (from iron peak and α-elements). A metallicity gradient of -0.22 ± 0.06 dex/R 25 is detected. The central metallicity on a logarithmic scale relative to the Sun is [Z] = -0.37 ± 0.03. A chemical evolution model using the observed distribution of column densities of the stellar and interstellar medium gas mass reproduces the observed metallicity distribution well and reveals a recent history of strong galactic mass accretion and wind outflows with accretion and mass-loss rates of the order of the star formation rate. There is an indication of spatial inhomogeneity in metallicity. In addition, the relatively high central metallicity of the disk confirms that two extraplanar metal-poor H ii regions detected in previous work 1.13 to 2.22 kpc above the galactic plane are ionized by massive stars formed in situ outside the disk. For a subsample of supergiants, for which Hubble Space Telescope photometry is available, the flux-weighted gravity-luminosity relationship is used to determine a distance modulus of 26.85 ± 0.10 mag.

  16. The H alpha Galaxy Survey VII. The spatial distribution of star formation within disks and bulges

    CERN Document Server

    James, P A; Knapen, J H

    2009-01-01

    We analyse the current build-up of stellar mass within the disks and bulges of nearby galaxies through a comparison of the spatial distributions of forming and old stellar populations. H alpha and R-band imaging are used to determine the distributions of young and old stellar populations in 313 S0a - Im field galaxies out to 40 Mpc. Concentration indices and mean normalised light profiles are calculated as a function of galaxy type and bar classification. The mean profiles and concentration indices show a strong and smooth dependence on galaxy type. Apart from a central deficit due to bulge/bar light in some galaxy types, mean H alpha and R-band profiles are very similar. Mean profiles within a given type are remarkably constant even given wide ranges in galaxy luminosity and size. SBc, SBbc and particularly SBb galaxies have profiles that are markedly different from those of unbarred galaxies. H alpha emission from SBb galaxies is studied in detail; virtually all show resolved central components and concentr...

  17. The AGORA High-Resolution Galaxy Simulations Comparison Project. II: Isolated Disk Test

    CERN Document Server

    Kim, Ji-hoon; Teyssier, Romain; Butler, Michael J; Ceverino, Daniel; Choi, Jun-Hwan; Feldmann, Robert; Keller, Ben W; Lupi, Alessandro; Quinn, Thomas; Revaz, Yves; Wallace, Spencer; Gnedin, Nickolay Y; Leitner, Samuel N; Shen, Sijing; Smith, Britton D; Thompson, Robert; Turk, Matthew J; Abel, Tom; Arraki, Kenza S; Benincasa, Samantha M; Chakrabarti, Sukanya; DeGraf, Colin; Dekel, Avishai; Goldbaum, Nathan J; Hopkins, Philip F; Hummels, Cameron B; Klypin, Anatoly; Li, Hui; Madau, Piero; Mandelker, Nir; Mayer, Lucio; Nagamine, Kentaro; Nickerson, Sarah; O'Shea, Brian W; Primack, Joel R; Roca-Fàbrega, Santi; Semenov, Vadim; Shimizu, Ikkoh; Simpson, Christine M; Todoroki, Keita; Wadsley, James W; Wise, John H

    2016-01-01

    Using an isolated Milky Way-mass galaxy simulation, we compare results from 9 state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relati...

  18. Near-infrared and optical broadband surface photometry of 86 face-on disk dominated galaxies .3. The statistics of the disk and bulge parameters

    NARCIS (Netherlands)

    deJong, RS

    1996-01-01

    The statistics of the fundamental bulge and disk parameters of galaxies and their relation to the Hubble sequence were investigated by an analysis of optical and near-infrared observations of 86 face-on spiral galaxies. The availability of near-infrared K passband data made it possible for the first

  19. The Formation of a Milky Way-size Disk Galaxy 1. A Comparison of Numerical Methods

    CERN Document Server

    Zhu, Qirong

    2016-01-01

    The long-standing challenge of creating a Milky Way-like disk galaxy from cosmological simulations has motivated significant developments in both numerical methods and physical models in recent years. We investigate these two fundamental aspects in a new comparison project using a set of cosmological hydrodynamic simulations of the formation and evolution of a Milky Way-size galaxy. In this study, we focus on the comparison of two particle-based hydrodynamics methods: the improved smoothed particle hydrodynamics (SPH) code Gadget, and the Lagrangian Meshless Finite-Mass (MFM) code GIZMO. All the simulations in this paper use the same initial conditions and physical models, which include physics of both dark matter and baryons, star formation, "energy-driven" outflow, metal-dependent cooling, stellar evolution and metal enrichment from supernovae. We find that both numerical schemes produce a late-type galaxy with extended gaseous and stellar disks. However, notable differences are present in a wide range of g...

  20. Formation of Nuclear Disks and Supermassive Black Hole Binaries in Multi-Scale Hydrodynamical Galaxy Mergers

    CERN Document Server

    Mayer, Lucio; Escala, Andres

    2008-01-01

    (Abridged) We review the results of the first multi-scale, hydrodynamical simulations of mergers between galaxies with central supermassive black holes (SMBHs) to investigate the formation of SMBH binaries in galactic nuclei. We demonstrate that strong gas inflows produce nuclear disks at the centers of merger remnants whose properties depend sensitively on the details of gas thermodynamics. In numerical simulations with parsec-scale spatial resolution in the gas component and an effective equation of state appropriate for a starburst galaxy, we show that a SMBH binary forms very rapidly, less than a million years after the merger of the two galaxies. Binary formation is significantly suppressed in the presence of a strong heating source such as radiative feedback by the accreting SMBHs. We also present preliminary results of numerical simulations with ultra-high spatial resolution of 0.1 pc in the gas component. These simulations resolve the internal structure of the resulting nuclear disk down to parsec sca...

  1. Galactic winds driven by isotropic and anisotropic cosmic ray diffusion in disk galaxies

    CERN Document Server

    Pakmor, Ruediger; Simpson, Christine M; Springel, Volker

    2016-01-01

    The physics of cosmic rays (CR) is a promising candidate for explaining the driving of galactic winds and outflows. Recent galaxy formation simulations have demonstrated the need for active CR transport either in the form of diffusion or streaming to successfully launch winds in galaxies. However, due to computational limitations, most previous simulations have modeled CR transport isotropically. Here, we discuss high resolution simulations of isolated disk galaxies in a $10^{11}\\rm{M_\\odot}$ halo with the moving mesh code {\\sc Arepo} that include injection of CRs from supernovae, advective transport, CR cooling, and CR transport through isotropic or anisotropic diffusion. We show that either mode of diffusion leads to the formation of strong bipolar outflows. However, they develop significantly later in the simulation with anisotropic diffusion compared to the simulation with isotropic diffusion. Moreover, we find that isotropic diffusion allows most of the CRs to quickly diffuse out of the disk, while in th...

  2. THE ACS NEARBY GALAXY SURVEY TREASURY. XI. THE REMARKABLY UNDISTURBED NGC 2403 DISK

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Benjamin F.; Dalcanton, Julianne J.; Stilp, Adrienne; Radburn-Smith, David [Department of Astronomy, Box 351580, University of Washington, Seattle, WA 98195 (United States); Dolphin, Andrew [Raytheon, 1151 E. Hermans Road, Tucson, AZ 85706 (United States); Skillman, Evan D., E-mail: ben@astro.washington.edu, E-mail: jd@astro.washington.edu, E-mail: adrienne@astro.washington.edu, E-mail: dolphin@raytheon.com, E-mail: skillman@astro.umn.edu [Department of Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States)

    2013-03-10

    We present detailed analysis of color-magnitude diagrams of NGC 2403, obtained from a deep (m {approx}< 28) Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observation of the outer disk of NGC 2403, supplemented by several shallow (m {approx}< 26) HST Advanced Camera for Surveys fields. We derive the spatially resolved star formation history of NGC 2403 out to 11 disk scale lengths. In the inner portions of the galaxy, we compare the recent star formation rates (SFRs) we derive from the resolved stars with those measured using GALEX FUV + Spitzer 24{mu} fluxes, finding excellent agreement between the methods. Our measurements also show that the radial gradient in recent SFR mirrors the disk exponential profile to 11 scale lengths with no break, extending to SFR densities a factor of {approx}100 lower than those that can be measured with GALEX and Spitzer ({approx}2 Multiplication-Sign 10{sup -6} M{sub Sun} yr{sup -1} kpc{sup -2}). Furthermore, we find that the cumulative stellar mass of the disk was formed at similar times at all radii. We compare these characteristics of NGC 2403 to those of its ''morphological twins'', NGC 300 and M 33, showing that the structure and age distributions of the NGC 2403 disk are more similar to those of the relatively isolated system NGC 300 than to those of the Local Group analog M 33. We also discuss the environments and HI morphologies of these three nearby galaxies, comparing them to integrated light studies of larger samples of more distant galaxy disks. Taken together, the physical properties and evolutionary history of NGC 2403 suggest that the galaxy has had no close encounters with other M 81 group members and may be falling into the group for the first time.

  3. Magnetohydrodynamic Simulations of Disk GalaxyFormation: the Magnetization of The Cold and Warm Medium

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Peng; Abel, Tom; /KIPAC, Menlo Park /Santa Barbara, KITP

    2007-12-18

    Using magnetohydrodynamic (MHD) adaptive mesh refinement simulations, we study the formation and early evolution of disk galaxies with a magnetized interstellar medium. For a 10{sup 10} M{sub {circle_dot}} halo with initial NFW dark matter and gas profiles, we impose a uniform 10{sup -9} G magnetic field and follow its collapse, disk formation and evolution up to 1 Gyr. Comparing to a purely hydrodynamic simulation with the same initial condition, we find that a protogalactic field of this strength does not significantly influence the global disk properties. At the same time, the initial magnetic fields are quickly amplified by the differentially rotating turbulent disk. After the initial rapid amplification lasting {approx} 500 Myr, subsequent field amplification appears self-regulated. As a result, highly magnetized material begin to form above and below the disk. Interestingly, the field strengths in the self-regulated regime agrees well with the observed fields in the Milky Way galaxy both in the warm and the cold HI phase and do not change appreciably with time. Most of the cold phase shows a dispersion of order ten in the magnetic field strength. The global azimuthal magnetic fields reverse at different radii and the amplitude declines as a function of radius of the disk. By comparing the estimated star formation rate (SFR) in hydrodynamic and MHD simulations, we find that after the magnetic field strength saturates, magnetic forces provide further support in the cold gas and lead to a decline of the SFR.

  4. The ACS Nearby Galaxy Survey Treasury VI. The Ancient Star Forming disk of NGC 404

    CERN Document Server

    Williams, Benjamin F; Gilbert, Karoline M; Stilp, Adrienne; Dolphin, Andrew; Seth, Anil C; Weisz, Daniel; Skillman, Evan

    2010-01-01

    We present HST/WFPC2 observations across the disk of the nearby isolated dwarf S0 galaxy NGC 404, which hosts an extended gas disk. Our deepest field reaches the red clump and main-sequence stars with ages 10 Gyr) population. Detailed modeling of the color-magnitude diagram suggests that ~70% of the stellar mass in the NGC 404 disk formed by z~2 (10 Gyr ago) and at least ~90% formed prior to z~1 (8 Gyr ago). These results indicate that the stellar populations of the NGC 404 disk are on average significantly older than those of other nearby disk galaxies, suggesting that early and late type disks may have different long-term evolutionary histories, not simply differences in their recent star formation rates. Comparisons of the spatial distribution of the young stellar mass and FUV emission in GALEX images show that the brightest FUV regions contain the youngest stars, but that some young stars (<160 Myr) lie outside of these regions. FUV luminosity appears to be strongly affected by both age and stellar mas...

  5. 3D Spectroscopy of Local Luminous Compact Blue Galaxies: Kinematic Maps of a Sample of 22 Objects

    CERN Document Server

    Pérez-Gallego, J; Castillo-Morales, A; Gallego, J; Castander, F J; Garland, C A; Gruel, N; Pisano, D J; Zamorano, J

    2011-01-01

    We use three dimensional optical spectroscopy observations of a sample of 22 local Luminous Compact Blue Galaxies (LCBGs) to create kinematic maps. By means of these, we classify the kinematics of these galaxies into three different classes: rotating disk (RD), perturbed rotation (PR), and complex kinematics (CK). We find 48% are RDs, 28% are PRs, and 24% are CKs. RDs show rotational velocities that range between $\\sim50$ and $\\sim200 km s^{-1}$, and dynamical masses that range between $\\sim1\\times10^{9}$ and $\\sim3\\times10^{10} M_{\\odot}$. We also address the following two fundamental questions through the study of the kinematic maps: \\emph{(i) What processes are triggering the current starbust in LCBGs?} We search our maps of the galaxy velocity fields for signatures of recent interactions and close companions that may be responsible for the enhanced star formation in our sample. We find 5% of objects show evidence of a recent major merger, 10% of a minor merger, and 45% of a companion. This argues in favor...

  6. The WHIQII Survey: Metallicities and Spectroscopic Properties of Luminous Compact Blue Galaxies

    CERN Document Server

    Tollerud, Erik J; van Zee, Liese; Cooke, Jeff

    2009-01-01

    As part of the WIYN High Image Quality Indiana Irvine (WHIQII) survey, we present 123 spectra of emission-line galaxies, selected on intermediate redshift (.4galaxies with blue colors that appear physically compact. The sample includes 15 true Luminous Compact Blue Galaxies (LCBGs) and an additional 27 slightly less extreme emission-line systems. These galaxies represent a highly evolving class that may play an important role in the decline of star formation since z~1, but their exact nature and evolutionary pathways remain a mystery. Here, we use emission lines to determine metallicities and ionization parameters, constraining their intrinsic properties and state of star formation. Some LCBG metallicities are consistent with a "bursting dwarf" scenario, while a substantial fraction of others are not, further confirming that LCBGs are a highly heterogeneous population but are broadly consistent with the intermediate redshift field. In agreement with previous studies, we observe overall evolution ...

  7. VizieR Online Data Catalog: Spectra of blue compact galaxies (Kong+, 2002)

    Science.gov (United States)

    Kong, X.; Cheng, F. Z.; Weiss, A.; Charlot, S.

    2003-08-01

    This is the second paper in a series studying the star formation rates, stellar components, metallicities, and star formation histories and evolution of a sample of blue compact galaxies. We analyzed spectral properties of 97 blue compact galaxies, obtained with the Beijing Astronomical Observatory (China) 2.16m telescope, with spectral range 3580{AA}-7400{AA}. We classify the spectra according to their emission lines: 13 of the total 97 BCG sample are non-emission line galaxies (non-ELGs); 10 have AGN-like emission (AGNs), and 74 of them are star-forming galaxies (SFGs). Emission line fluxes and equivalent widths, continuum fluxes, the 4000A Balmer break index and equivalent widths of absorption lines are measured from the spectra. Please find more detail information in http://optik2.mtk.nao.ac.jp/~xkong/bcg/ (5 data files).

  8. LoCuSS: Exploring the selection of faint blue background galaxies for cluster weak-lensing

    CERN Document Server

    Ziparo, Felicia; Okabe, Nobuhiro; Haines, Chris P; Pereira, Maria J; Egami, Eiichi

    2015-01-01

    Cosmological constraints from galaxy clusters rely on accurate measurements of the mass and internal structure of clusters. An important source of systematic uncertainty in cluster mass and structure measurements is the secure selection of background galaxies that are gravitationally lensed by clusters. This issue has been shown to be particular severe for faint blue galaxies. We therefore explore the selection of faint blue background galaxies, by reference to photometric redshift catalogs derived from the COSMOS survey and our own observations of massive galaxy clusters at z~0.2. We show that methods relying on photometric redshifts of galaxies in/behind clusters based on observations through five filters, and on deep 30-band COSMOS photometric redshifts are both inadequate to identify safely faint blue background galaxies. This is due to the small number of filters used by the former, and absence of massive galaxy clusters at redshifts of interest in the latter. We therefore develop a pragmatic method to c...

  9. Stellar population gradients in Fornax Cluster S0 galaxies: connecting bulge and disk evolution

    CERN Document Server

    Bedregal, A G; Aragón-Salamanca, A; Merrifield, M R

    2011-01-01

    We present absorption-line index gradients for a sample of S0 galaxies in the Fornax Cluster. The sample has been selected to span a wide range in galaxy mass, and the deep VLT-FORS2 spectroscopy allows us to explore the stellar populations all the way to the outer disk-dominated regions of these galaxies. We find that globally, in both bulges and disks, star formation ceased earliest in the most massive systems, as a further manifestation of downsizing. However, within many galaxies, we find an age gradient which indicates that star formation ended first in the outermost regions. Metallicity gradients, when detected, are always negative such that the galaxy centres are more metal-rich. This finding fits with a picture in which star formation continued in the central regions, with enriched material, after it had stopped in the outskirts. Age and metallicity gradients are correlated, suggesting that large differences in star formation history between the inner and outer parts of S0 galaxies yield large differe...

  10. The Catalog of Edge-on Disk Galaxies from SDSS. Part I: the catalog and the Structural Parameters of Stellar Disks

    CERN Document Server

    Bizyaev, D V; Mosenkov, A V; Reshetnikov, V P; Sotnikova, N Ya; Yablokova, N V; Hillyer, R W

    2014-01-01

    We present a catalog of true edge-on disk galaxies automatically selected from the Seventh Data Release (DR7) of the Sloan Digital Sky Survey. A visual inspection of the $g$, $r$ and $i$ images of about 15000 galaxies allowed us to split the initial sample of edge-on galaxy candidates into 4768 (31.8% of the initial sample) genuine edge-on galaxies, 8350 (55.7%) non-edge-ons, and 1865 (12.5%) edge-on galaxies not suitable for simple automatic analysis because these objects show signs of interaction, warps, or nearby bright stars project on it. We added more candidate galaxies from RFGC, EFIGI, RC3, and Galaxy Zoo catalogs found in the SDSS footprints. Our final sample consists of 5747 genuine edge-on galaxies. We estimate the structural parameters of the stellar disks (the stellar disk thickness, radial scale length, and central surface brightness) in the galaxies by analyzing photometric profiles in each of the g, r, and i images. We also perform simplified 3-D modeling of the light distribution in the stell...

  11. SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves

    Science.gov (United States)

    Lelli, Federico; McGaugh, Stacy S.; Schombert, James M.

    2016-12-01

    We introduce SPARC (Spitzer Photometry and Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 μm and high-quality rotation curves from previous H i/Hα studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (∼5 dex), and surface brightnesses (∼4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass–H i mass relation and the stellar radius–H i radius relation have significant intrinsic scatter, while the H i mass–radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic to observed velocity (V bar/V obs) for different characteristic radii and values of the stellar mass-to-light ratio (ϒ⋆) at [3.6]. Assuming ϒ⋆ ≃ 0.5 M ⊙/L ⊙ (as suggested by stellar population models), we find that (i) the gas fraction linearly correlates with total luminosity (ii) the transition from star-dominated to gas-dominated galaxies roughly corresponds to the transition from spiral galaxies to dwarf irregulars, in line with density wave theory; and (iii) V bar/V obs varies with luminosity and surface brightness: high-mass, high-surface-brightness galaxies are nearly maximal, while low-mass, low-surface-brightness galaxies are submaximal. These basic properties are lost for low values of ϒ⋆ ≃ 0.2 M ⊙/L ⊙ as suggested by the DiskMass survey. The mean maximum-disk limit in bright galaxies is ϒ⋆ ≃ 0.7 M ⊙/L ⊙ at [3.6]. The SPARC data are publicly available and represent an ideal test bed for models of galaxy formation.

  12. Cannibals in the thick disk: the young α-rich stars as evolved blue stragglers

    Science.gov (United States)

    Jofré, P.; Jorissen, A.; Van Eck, S.; Izzard, R. G.; Masseron, T.; Hawkins, K.; Gilmore, G.; Paladini, C.; Escorza, A.; Blanco-Cuaresma, S.; Manick, R.

    2016-10-01

    Spectro-seismic measurements of red giants enabled the recent discovery of stars in the thick disk that are more massive than 1.4 M⊙. While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 "young" stars and 13 "old" stars with similar stellar parameters but with masses below 1.2 M⊙ and found that more of the young starsappear to be in binary systems with respect to the old stars.Furthermore, we show that the young stars do not follow the expected trend of [C/H] ratios versus mass for individual stars. However, with a population synthesis of low-mass stars including binary evolution and mass transfer, we can reproduce the observed [C/N] ratios versus mass. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study the evolution of field blue stragglers after they have left the main-sequence.

  13. Spectroscopic Study of Blue Compact Galaxies II. Spectral Analysis and Correlations

    CERN Document Server

    Kong, X; Weiss, A; Charlot, S

    2002-01-01

    This is the second paper in a series studying the star formation rates, stellar components, metallicities, and star formation histories and evolution of a sample of blue compact galaxies. We analyzed spectral properties of 97 blue compact galaxies, obtained with the Beijing Astronomical Observatory (China) 2.16 m telescope, with spectral range 3580\\AA -- 7400\\AA. We classify the spectra according to their emission lines: 13 of the total 97 BCGs sample are non-emission line galaxies (non-ELGs); 10 have AGN-like emission (AGNs), and 74 of them are star-forming galaxies (SFGs). Emission line fluxes and equivalent widths, continuum fluxes, the 4000 \\AA Balmer break index and equivalent widths of absorption lines are measured from the spectra. We investigate the emission line trends in the integrated spectra of the star-forming galaxies in our sample, and find that: 1) The equivalent widths of emission lines are correlated with the galaxy absolute blue magnitude $M_B$; lower luminosity systems tend to have larger ...

  14. The rapid formation of a large rotating disk galaxy three billion years after the Big Bang.

    Science.gov (United States)

    Genzel, R; Tacconi, L J; Eisenhauer, F; Schreiber, N M Förster; Cimatti, A; Daddi, E; Bouché, N; Davies, R; Lehnert, M D; Lutz, D; Nesvadba, N; Verma, A; Abuter, R; Shapiro, K; Sternberg, A; Renzini, A; Kong, X; Arimoto, N; Mignoli, M

    2006-08-17

    Observations and theoretical simulations have established a framework for galaxy formation and evolution in the young Universe. Galaxies formed as baryonic gas cooled at the centres of collapsing dark-matter haloes; mergers of haloes and galaxies then led to the hierarchical build-up of galaxy mass. It remains unclear, however, over what timescales galaxies were assembled and when and how bulges and disks--the primary components of present-day galaxies--were formed. It is also puzzling that the most massive galaxies were more abundant and were forming stars more rapidly at early epochs than expected from models. Here we report high-angular-resolution observations of a representative luminous star-forming galaxy when the Universe was only 20% of its current age. A large and massive rotating protodisk is channelling gas towards a growing central stellar bulge hosting an accreting massive black hole. The high surface densities of gas, the high rate of star formation and the moderately young stellar ages suggest rapid assembly, fragmentation and conversion to stars of an initially very gas-rich protodisk, with no obvious evidence for a major merger.

  15. Mapping the inner regions of the polar disk galaxy NGC4650A with MUSE

    CERN Document Server

    Iodice, E; Combes, F; de Zeeuw, T; Arnaboldi, M; Weilbacher, P M; Bacon, R; Kuntschner, H; Spavone, M

    2015-01-01

    [abridged] The polar disk galaxy NGC4650A was observed during the commissioning of the MUSE at the ESO VLT to obtain the first 2D map of the velocity and velocity dispersion for both stars and gas. The new MUSE data allow the analysis of the structure and kinematics towards the central regions of NGC4650A, where the two components co-exist. These regions were unexplored by the previous long-slit literature data available for this galaxy. The extended view of NGC~4650A given by the MUSE data is a galaxy made of two perpendicular disks that remain distinct and drive the kinematics right into the very centre of this object. In order to match this observed structure for NGC4650A, we constructed a multicomponent mass model made by the combined projection of two disks. By comparing the observations with the 2D kinematics derived from the model, we found that the modelled mass distribution in these two disks can, on average, account for the complex kinematics revealed by the MUSE data, also in the central regions of...

  16. Evidence of Nuclear Disks from the Radial Distribution of CCSNe in Starburst Galaxies

    Science.gov (United States)

    Herrero-Illana, Rubén; Pérez-Torres, Miguel Ángel; Alberdi, Antxon

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ˜ 100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (≲ 0.'1) radio observations. We derived scale-length values for the putative nuclear disks, which range from ˜ 20-30 pc for Arp 299-A and Arp 220, up to ˜ 140 pc for M82. The radial distribution of SNe for the nuclear disks in Arp 299-A and Arp 220 is also consistent with a power-law surface density profile of exponent γ = 1, as expected from detailed hydrodynamical simulations of nuclear disks. This study is detailed in Herrero-Illana, Perez-Torres, and Alberdi [11].

  17. Circumnuclear molecular gas in megamaser disk galaxies NGC 4388 and NGC 1194

    Energy Technology Data Exchange (ETDEWEB)

    Greene, Jenny E. [Department of Astrophysics, Princeton University, Princeton, NJ 08540 (United States); Seth, Anil [University of Utah, Salt Lake City, UT 84112 (United States); Lyubenova, Mariya; Van de Ven, Glenn; Läsker, Ronald [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Walsh, Jonelle [Department of Astronomy, The University of Texas at Austin, 2515 Speedway, Stop C1400, Austin, TX 78712-1205 (United States)

    2014-06-20

    We explore the warm molecular and ionized gas in the centers of two megamaser disk galaxies using K-band spectroscopy. Our ultimate goal is to determine how gas is funneled onto the accretion disk, here traced by megamaser spots on sub-parsec scales. We present NIR IFU data with a resolution of ∼50 pc for two galaxies: NGC 4388 with VLT/SINFONI and NGC 1194 with Keck/OSIRIS+AO. The high spatial resolution and rich spectral diagnostics allow us to study both the stellar and gas kinematics as well as gas excitation on scales only an order of magnitude larger than the maser disk. We find a drop in the stellar velocity dispersion in the inner ∼100 pc of NGC 4388, a common signature of a dynamically cold central component seen in many active nuclei. We also see evidence for noncircular gas motions in the molecular hydrogen on similar scales, with the gas kinematics on 100 parsec scales aligned with the megamaser disk. In contrast, the high ionization lines and Brγ trace outflow along the 100 parsec-scale jet. In NGC 1194, the continuum from the accreting black hole is very strong, making it difficult to measure robust two-dimensional kinematics, but the spatial distribution and line ratios of the molecular hydrogen and Brγ have consistent properties between the two galaxies.

  18. The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

    Science.gov (United States)

    Lelli, Federico; McGaugh, Stacy S.; Schombert, James M.; Pawlowski, Marcel S.

    2016-08-01

    We use the Spitzer Photometry and Accurate Rotation Curves database to study the relation between the central surface density of stars {{{Σ }}}\\star (0) and dynamical mass {{{Σ }}}{{dyn}}(0) in 135 disk galaxies (S0 to dIrr). We find that {{{Σ }}}{{dyn}}(0) correlates tightly with {{{Σ }}}\\star (0) over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness (LSB) galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (˜0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.

  19. The Relation between Stellar and Dynamical Surface Densities in the Central Regions of Disk Galaxies

    CERN Document Server

    Lelli, Federico; Schombert, James M; Pawlowski, Marcel S

    2016-01-01

    We use the SPARC (Spitzer Photometry & Accurate Rotation Curves) database to study the relation between the central surface density of stars Sstar and dynamical mass Sdyn in 135 disk galaxies (S0 to dIrr). We find that Sdyn correlates tightly with Sstar over 4 dex. This central density relation can be described by a double power law. High surface brightness galaxies are consistent with a 1:1 relation, suggesting that they are self-gravitating and baryon dominated in the inner parts. Low surface brightness galaxies systematically deviate from the 1:1 line, indicating that the dark matter contribution progressively increases but remains tightly coupled to the stellar one. The observed scatter is small (~0.2 dex) and largely driven by observational uncertainties. The residuals show no correlations with other galaxy properties like stellar mass, size, or gas fraction.

  20. M82 AS A GALAXY: MORPHOLOGY AND STELLAR CONTENT OF THE DISK AND HALO

    Directory of Open Access Journals (Sweden)

    Y. D. Mayya

    2009-01-01

    Full Text Available For decades, the nuclear starburst has taken all the limelight in M82 with very little discussion on M82 as a galaxy. The situation is changing over the last decade, with the publication of some important results on the morphology and stellar content of its disk and halo. In this review, we discuss these recent ndings in the framework of M82 as a galaxy. It is known for almost half a century that M82 as a galaxy doesn't follow the trends expected for normal galaxies that had prompted the morphologists to introduce a separate morphological type under the name Irr II or amorphous. It is now being understood that the main reasons behind its apparently distinct morphological appearance are its peculiar star formation history, radial distribution of gas density and the form of the rotation curve. The disk formed almost all of its stars through a burst mode around 500 Myr ago, with the disk star formation completely quenched around 100 Myr ago. The fossil record of the disk-wide burst lies in the form of hundreds of compact star clusters, similar in mass to that of the globular clusters in the Milky Way, but an order of magnitude younger. The present star formation is restricted entirely to the central 500 pc zone, that contains more than 200 young compact star clusters. The disk contains a non-star-forming spiral arm, hidden from the optical view by a combination of extinction and high inclination to the line of sight. The halo of M82 is also unusual in its stellar content, with evidence for star formation, albeit at low levels, occurring continuously for over a gigayear. We carefully examine each of the observed abnormality to investigate the overall e ect of interaction on the evolution of M82.

  1. Hydrodynamic vortices in the gaseous disks of galaxies

    Science.gov (United States)

    Antonov, V. A.; Zhelezniak, O. A.

    1989-08-01

    A two-dimensional gas stream with a velocity field vx proportional to y is considered which is assumed to be stationary with respect to a rotating coordinate system. This stream can serve as a model of the local kinematic of a galactic gaseous disk. It is shown the local uniform stream cannot develop into a soliton if self-gravitation, dissipation, and the nonuniformity of the vortex are neglected.

  2. The Imprint of Radial Migration on the Vertical Structure of Galaxy Disks

    Science.gov (United States)

    Vera-Ciro, Carlos; D'Onghia, Elena; Navarro, Julio F.

    2016-12-01

    We use numerical simulations to examine the effects of radial migration on the vertical structure of galaxy disks. The simulations follow three exponential disks of different mass but similar circular velocity, radial scalelength, and (constant) scale height. The disks develop different non-axisymmetric patterns, ranging from feeble, long-lived multiple arms to strong, rapidly evolving few-armed spirals. These fluctuations induce radial migration through secular changes in the angular momentum of disk particles, mixing the disk radially and blurring pre-existing gradients. Migration primarily affects stars with small vertical excursions, regardless of spiral pattern. This “provenance bias” largely determines the vertical structure of migrating stars: inward migrators thin down as they move in, whereas outward migrators do not thicken up but rather preserve the disk scale height at their destination. Migrators of equal birth radius thus develop a strong scale-height gradient, not by flaring out as commonly assumed, but by thinning down as they spread inward. Similar gradients have been observed for low-[α/Fe] mono-abundance populations (MAPs) in the Galaxy, but our results argue against interpreting them as a consequence of radial migration. This is because outward migration does not lead to thickening, implying that the maximum scale height of any population should reflect its value at birth. In contrast, Galactic MAPs have scale heights that increase monotonically outward, reaching values that greatly exceed those at their presumed birth radii. Given the strong vertical bias affecting migration, a proper assessment of the importance of radial migration in the Galaxy should take carefully into account the strong radial dependence of the scale heights of the various stellar populations.

  3. Modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies

    Institute of Scientific and Technical Information of China (English)

    James Q. Feng; C. F. Gallo

    2011-01-01

    We present an efficient,robust computational method for modeling the Newtonian dynamics for rotation curve analysis of thin-disk galaxies.With appropriate mathematical treatments,the apparent numerical difficulties associated with singularities in computing elliptic integrals are completely removed.Using a boundary element discretization procedure,the governing equations are transformed into a linear algebra matrix equation that can be solved by straightforward Gauss elimination in one step without further iterations.The numerical code implemented according to our algorithm can accurately determine the surface mass density distribution in a disk galaxy from a measured rotation curve (or vice versa).For a disk galaxy with a typical fiat rotation curve,our modeling results show that the surface mass density monotonically decreases from the galactic center toward the periphery,according to Newtonian dynamics.In a large portion of the galaxy,the surface mass density follows an approximately exponential law of decay with respect to the galactic radial coordinate.Yet the radial scale length for the surface mass density seems to be generally larger than that of the measured brightness distribution,suggesting an increasing mass-to- light ratio with the radial distance in a disk galaxy.In a nondimensionalized form,our mathematical system contains a dimensionless parameter which we call the “galactic rotation number” that represents the gross ratio of centrifugal force and gravitational force.The value of this galactic rotation number is determined as part of the numerical solution.Through a systematic computational analysis,we have illustrated that the galactic rotation number remains within ±10% of 1.70 for a wide variety of rotation curves.This implies that the total mass in a disk galaxy is proportional to V(0)2 Rg,with V(0) denoting the characteristic rotation velocity (such as the “fiat” value in a typical rotation curve) and Rg the radius of the galactic

  4. Star formation and accretion in the circumnuclear disks of active galaxies

    CERN Document Server

    Wutschik, Stephanie; Palmer, Thomas S

    2013-01-01

    We explore the evolution of supermassive black holes (SMBH) centered in a circumnuclear disk (CND) as a function of the mass supply from the host galaxy and considering different star formation laws, which may give rise to a self-regulation via the injection of supernova-driven turbulence. A system of equations describing star formation, black hole accretion and angular momentum transport was solved for an axisymmetric disk in which the gravitational potential includes contributions from the black hole, the disk and the hosting galaxy. Our model extends the framework provided by Kawakatu et al. (2008) by separately considering the inner and outer part of the disk, and by introducing a potentially non-linear dependence of the star formation rate on the gas surface density and the turbulent velocity. The star formation recipes are calibrated using observational data for NGC 1097, while the accretion model is based on turbulent viscosity as a source of angular momentum transport in a thin viscous accretion disk....

  5. Properties of Bulgeless Disk Galaxies II. Star Formation as a Function of Circular Velocity

    CERN Document Server

    Watson, Linda C; Lisenfeld, Ute; Wong, Man-Hong; Boeker, Torsten; Schinnerer, Eva

    2012-01-01

    We study the relation between the surface density of gas and star formation rate in twenty moderately-inclined, bulgeless disk galaxies (Sd-Sdm Hubble types) using CO(1-0) data from the IRAM 30m telescope, HI emission line data from the VLA/EVLA, H-alpha data from the MDM Observatory, and PAH emission data derived from Spitzer IRAC observations. We specifically investigate the efficiency of star formation as a function of circular velocity (v_circ). Previous work found that the vertical dust structure and disk stability of edge-on, bulgeless disk galaxies transition from diffuse dust lanes with large scale heights and gravitationally-stable disks at v_circ 120 km/s. We find no transition in star formation efficiency (Sigma_SFR/Sigma_HI+H2) at v_circ = 120 km/s, or at any other circular velocity probed by our sample (v_circ = 46 - 190 km/s). Contrary to previous work, we find no transition in disk stability at any circular velocity in our sample. Assuming our sample has the same dust structure transition as t...

  6. Magnetohydrodynamic Simulations of Disk Galaxy Formation: the Magnetization of The Cold and Warm Medium

    CERN Document Server

    Wang, Peng

    2007-01-01

    Using magnetohydrodynamic (MHD) adaptive mesh refinement simulations, we study the formation and early evolution of disk galaxies with a magnetized interstellar medium. For a $10^{10}$ \\msun halo with initial NFW dark matter and gas profiles, we impose a uniform $10^{-9}$ G magnetic field and follow its collapse, disk formation and evolution up to 1 Gyr. Comparing to a purely hydrodynamic simulation with the same initial condition, we find that a protogalactic field of this strength does not significantly influence the global disk properties. At the same time, the initial magnetic fields are quickly amplified by the differentially rotating turbulent disk. After the initial rapid amplification lasting $\\sim500$ Myr, subsequent field amplification appears self-regulated. As a result, highly magnetized material begin to form above and below the disk. Interestingly, the field strengths in the self-regulated regime agrees well with the observed fields in the Milky Way galaxy both in the warm and the cold HI phase ...

  7. Cosmic-ray Driven Outflows in Global Galaxy Disk Models

    CERN Document Server

    Salem, Munier

    2013-01-01

    Galactic-scale winds are a generic feature of massive galaxies with high star formation rates across a broad range of redshifts. Despite their importance, a detailed physical understanding of what drives these mass-loaded global flows has remained elusive. In this paper, we explore the dynamical impact of cosmic rays by performing the first three-dimensional, adaptive mesh refinement simulations of an isolated starbursting galaxy that includes a basic model for the production, dynamics and diffusion of galactic cosmic rays. We find that including cosmic rays naturally leads to robust, massive, bipolar outflows from our 10^12 Msun halo, with a mass-loading factor Mout/SFR = 0.3 for our fiducial run. Other reasonable parameter choices led to mass-loading factors above unity. The wind is multiphase and is accelerated to velocities well in excess of the escape velocity. We employ a two-fluid model for the thermal gas and relativistic CR plasma and model a range of physics relevant to galaxy formation, including r...

  8. The flaring HI disk of the nearby spiral galaxy NGC 2683

    OpenAIRE

    Vollmer, B.; Nehlig, F.; Ibata, R.

    2015-01-01

    New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution ...

  9. Outside-in Shrinking of the Star-forming Disk of Dwarf Irregular Galaxies

    CERN Document Server

    Zhang, Hong-Xin; Elmegreen, Bruce G; Gao, Yu; Schruba, Andreas

    2011-01-01

    We have studied multi-band surface brightness profiles of a representative sample of 34 nearby dwarf irregular galaxies (dIrrs). Our data include GALEX FUV/NUV, UBV, H\\alpha, and Spitzer 3.6 \\mum images. These galaxies constitute the majority of the LITTLE THINGS survey. By modeling the azimuthal averages of the spectral energy distributions with a complete library of star formation (SF) histories, we derived the stellar mass surface density distributions and the SF rate averaged over three different timescales: the recent 0.1 Gyr, 1 Gyr and a Hubble time. We find that, for \\sim 80% (27 galaxies) of our sample galaxies, radial profiles (at least in the outer part) at shorter wavelengths have shorter disk scale lengths than those at longer wavelengths. This indicates that the star-forming disk has been shrinking. In addition, the radial distributions of the stellar mass surface density are well described as piece-wise exponential profiles, and \\sim 80% of the galaxies have steeper mass profiles in the outer di...

  10. Evidence of nuclear disks in starburst galaxies from their radial distribution of supernovae

    CERN Document Server

    Herrero-Illana, R; Alberdi, A

    2012-01-01

    Galaxy-galaxy interactions are expected to be responsible for triggering massive star formation and possibly accretion onto a supermassive black hole, by providing large amounts of dense molecular gas down to the central kiloparsec region. Several scenarios to drive the gas further down to the central ~100 pc, have been proposed, including the formation of a nuclear disk around the black hole, where massive stars would produce supernovae. Here, we probe the radial distribution of supernovae and supernova remnants in the nuclear regions of the starburst galaxies M82, Arp 299-A, and Arp 220, by using high-angular resolution (< 0."1) radio observations published in the literature (for M82 and Arp 220), or obtained by ourselves from the European VLBI Network (Arp 299-A). Our main goal was to characterize the nuclear starbursts in those galaxies and thus test scenarios that propose that nuclear disks of sizes ~100 pc form in the central regions of starburst galaxies. We obtained the radial distribution of super...

  11. Determination of the Thickness of Non-Edge-on Disk Galaxies

    Institute of Scientific and Technical Information of China (English)

    Ying-He Zhao; Qiu-He Peng; Lan Wang

    2004-01-01

    We propose a method to determine the thickness of non-edge-on disk galaxies from their observed structure of spiral arms, based on the solution of the truly three-dimensional Poisson's equation for a logarithmic disturbance of density and under the condition where the self-consistency of the density wave theory is no longer valid. From their measured number of arms, pitch angle and location of the innermost point of the spiral arms, we derive and present the thicknesses of 34spiral galaxies.

  12. Megamaser Disks Reveal a Broad Distribution of Black Hole Mass in Spiral Galaxies

    CERN Document Server

    Greene, Jenny E; Kim, Minjin; Laesker, Ronald; Goulding, Andy D; Gao, Feng; Braatz, James A; Henkel, Christian; Condon, James; Lo, Fred K Y; Zhao, Wei

    2016-01-01

    We use new precision measurements of black hole masses from water megamaser disks to investigate scaling relations between macroscopic galaxy properties and supermassive black hole (BH) mass. The megamaser-derived BH masses span 10^6-10^8 M_sun, while all the galaxy properties that we examine (including stellar mass, central mass density, central velocity dispersion) lie within a narrow range. Thus, no galaxy property correlates tightly with M_BH in ~L* spiral galaxies. Of them all, stellar velocity dispersion provides the tightest relation, but at fixed sigma* the mean megamaser M_BH are offset by -0.6+/-0.1 dex relative to early-type galaxies. Spiral galaxies with non-maser dynamical BH masses do not show this offset. At low mass, we do not yet know the full distribution of BH mass at fixed galaxy property; the non-maser dynamical measurements may miss the low-mass end of the BH distribution due to inability to resolve the spheres of influence and/or megamasers may preferentially occur in lower-mass BHs.

  13. NoSOCS in SDSS - V. Red disc and blue bulge galaxies across different environments

    Science.gov (United States)

    Lopes, P. A. A.; Rembold, S. B.; Ribeiro, A. L. B.; Nascimento, R. S.; Vajgel, B.

    2016-09-01

    We investigated the typical environment and physical properties of `red discs' and `blue bulges', comparing those to the `normal' objects in the blue cloud and red sequence. Our sample is composed of cluster members and field galaxies at z ≤ 0.1, so that we can assess the impact of the local and global environment. We find that disc galaxies display a strong dependence on environment, becoming redder for higher densities. This effect is more pronounced for objects within the virial radius, being also strong related to the stellar mass. We find that local and global environment affect galaxy properties, but the most effective parameter is stellar mass. We find evidence for a scenario where `blue discs' are transformed into `red discs' as they grow in mass and move to the inner parts of clusters. From the metallicity differences of red and blue discs, and the analysis of their star formation histories, we suggest the quenching process is slow. We estimate a quenching time-scale of ˜2-3 Gyr. We also find from the sSFR-M* plane that `red discs' gradually change as they move into clusters. The `blue bulges' have many similar properties than `blue discs', but some of the former show strong signs of asymmetry. The high asymmetry `blue bulges' display enhanced recent star formation compared to their regular counterparts. That indicates some of these systems may have increased their star formation due to mergers. None the less, there may not be a single evolutionary path for these blue early-type objects.

  14. The blue host galaxy of the red GRB 000418

    DEFF Research Database (Denmark)

    Gorosabel, J.; Klose, S.; Christensen, L.;

    2003-01-01

    (A(V) = 0.4-0.9 mag), suggesting a homogeneous distribution of the interstellar medium (ISM) in the host galaxy. These findings are supplemented by morphological information from Hubble Space Telescope (HST) imaging: the surface brightness profile is smooth, symmetric and compact with no underlying...

  15. The X-ray halo of an extremely luminous LSB disk galaxy

    Science.gov (United States)

    Weiner, Benjamin J.

    2004-01-01

    We are continuing to refine our upper limit on emission from halo gas in Malin 2. The upper limit is, of course, below the detected flux, but is made more difficult to quantify by the disk and possible AGN sources. We are also exploring spectral and spatial-size constraints to help separate the sources of emission. On the theory side, more recent work on the X-ray halo luminosity from halo gas leftover from galaxy formation has lowered the prediction for disk galaxies (e.g. Toft et al. 2002, MNRAS, 335, 799). While our upper limit is well below the original prediction, refinements in model have moved the theoretical goalposts, so that the observation may be consistent with newer models. A recent theoretical development, which our observations of Malin 2 appear to support, is that a substantial amount of mass can be accreted onto galaxies without being heated at a virial shock. The previous standard theory was that gas accreting into a halo hits a virial shock and is heated to high temperatures, which could produce X-ray halos in massive galaxies. Recent models show that "smooth accretion" of matter bypasses the virial shocking (Murali e t al. 2002, ApJ, 571, 1; Birnboim & Dekel 2003, MNRAS, 345, 349). Additionally, new hydrodynamical simulations of galaxy mergers by UCSC graduate student T. J. Cox show that hot gas halos can be created by gas blown out from the merger, taking up orbital energy of the merging galaxies (Cox et al. 2004, ApJ, 607, L87). If mergers rather than virial shocking are the origin of hot gas halos, the existence of an X-ray halo should depend more on past merger activity than halo mass. Then it makes sense that elliptical galaxies and poor groups with ellipticals, which are probably formed in mergers, have X-ray gas halos; while a giant, quiescent LSB disk galaxy like Malin 2, which has never suffered a major merger, does not have an X-ray halo. While both the observational expectations and theoretical models have changed since we began this

  16. The Formation of a Milky Way-sized Disk Galaxy. I. A Comparison of Numerical Methods

    Science.gov (United States)

    Zhu, Qirong; Li, Yuexing

    2016-11-01

    The long-standing challenge of creating a Milky Way- (MW-) like disk galaxy from cosmological simulations has motivated significant developments in both numerical methods and physical models. We investigate these two fundamental aspects in a new comparison project using a set of cosmological hydrodynamic simulations of an MW-sized galaxy. In this study, we focus on the comparison of two particle-based hydrodynamics methods: an improved smoothed particle hydrodynamics (SPH) code Gadget, and a Lagrangian Meshless Finite-Mass (MFM) code Gizmo. All the simulations in this paper use the same initial conditions and physical models, which include star formation, “energy-driven” outflows, metal-dependent cooling, stellar evolution, and metal enrichment. We find that both numerical schemes produce a late-type galaxy with extended gaseous and stellar disks. However, notable differences are present in a wide range of galaxy properties and their evolution, including star-formation history, gas content, disk structure, and kinematics. Compared to Gizmo, the Gadget simulation produced a larger fraction of cold, dense gas at high redshift which fuels rapid star formation and results in a higher stellar mass by 20% and a lower gas fraction by 10% at z = 0, and the resulting gas disk is smoother and more coherent in rotation due to damping of turbulent motion by the numerical viscosity in SPH, in contrast to the Gizmo simulation, which shows a more prominent spiral structure. Given its better convergence properties and lower computational cost, we argue that the MFM method is a promising alternative to SPH in cosmological hydrodynamic simulations.

  17. STAR FORMATION IN THE OUTER DISKS OF SPIRAL GALAXIES: ULTRAVIOLET AND H{alpha} PHOTOMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Kate L.; Van Zee, Liese [Department of Astronomy, Indiana University, Bloomington, IN 47405 (United States); Skillman, Evan D., E-mail: barneskl@astro.indiana.edu, E-mail: vanzee@astro.indiana.edu, E-mail: skillman@astro.umn.edu [Department of Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)

    2011-12-20

    We present an analysis of ultradeep UV and H{alpha} imaging of five nearby spiral galaxies to study the recent star formation in the outer disk. Using azimuthally averaged ellipse photometry as well as aperture photometry of individual young stellar complexes, we measure how star formation rates (SFRs) and UV and H{alpha} colors vary with radius. We detect azimuthally averaged UV flux to {approx}1.2-1.4 R{sub 25} in most galaxies; at the edge of the detected UV disk, the surface brightnesses are 28-29 mag arcsec{sup -2}, corresponding to SFR surface densities of {approx}3 Multiplication-Sign 10{sup -4} M{sub Sun} yr{sup -1} kpc{sup -2}. Additionally, we detect between 120 and 410 young stellar complexes per galaxy, with a significant number of detections out to {approx}1.5 R{sub 25}. We measure radial FUV-NUV profiles, and find that the dispersion in the UV colors of individual young stellar complexes increases with radius. We investigate how radial variations in the frequency of star formation episodes can create color gradients and increasing dispersion in the UV colors of star-forming regions, like those observed in our study. Specifically, we use recently published, high spatial and temporal resolution measurements of {Sigma}{sub SFR} throughout the disk of M33 to estimate the frequency of star formation episodes throughout the disk of a typical spiral galaxy. We use stellar synthesis models of these star formation histories (SFHs) to measure the variations in UV colors and find that we can replicate large dispersions in UV colors based on episodic SFHs.

  18. SPH code for dynamical and chemical evolution of disk galaxies

    CERN Document Server

    Berczik, P

    1998-01-01

    The problem of chemical and dynamical evolution of galaxies is one of the most attracting and complex problems of modern astrophysics. Within the framework of the given work the standard dynamic Smoothed Particle Hydrodynamics (SPH) code (Monaghan J.J. 1992, ARAA, 30, 543) is noticeably expanded. Our investigation concernes with the changes and incorporation of new ideas into the algorithmic inclusion of Star Formation (SF) and Super Novae (SN) explosions in SPH (Berczik P. & Kravchuk S.G., 1996, ApSpSci, 245, 27). The proposed energy criterion for definition of a place and efficiency of SF results in the successfully explain Star Formation History (SFH) in isolated galaxies of different types. On the base of original ideas we expand a code in a more realistic way of the description of effects of return of a hot, chemical enriched gas in Interstellar Matter (ISM). In addition to the account of SNII, we offer the self-agreed account of SNIa and PN. This allows to describe not only the ISM content of $ O^{1...

  19. Massive blue early-type galaxies in the SDSS. I. A new population of recently quenched elliptical galaxies

    CERN Document Server

    McIntosh, Daniel H; Cooper, Andrew; Bell, Eric F; Keres, Dusan; Bosch, Frank C van den; Gallazzi, Anna; Haines, Tim; Mann, Justin; Pasquali, Anna; Christian, Allison M

    2013-01-01

    We use the SDSS to explore early-type galaxies (ETGs) that are plausibly in transition between the red sequence and the blue cloud. Through careful morphological inspection, we identify 1500 unusually blue elliptical galaxies among a larger sample of blue ETGs with 0.011e10 h^{-2} M_sun. Blue ellipticals comprise 3.7% of all ETGs with 1e1050% of the expected quiescent growth at z~0 assuming this phase lasts 0.5Gyr. Based on color, stellar M/L ratios and metallicity estimates, we argue that RQEs have recent SFHs that differ from rejuvenated ETGs. Yet, a significant but small incidence (5%) of RQEs with E+A spectra implies that the quenching of most RQEs did not involve a large starburst. Most (90%) RQEs reside at the centers of 3x10^{12}h^{-1} M_sun groups, which agrees well with the `small group scale' in which spiral merging onto the halo center is maximally efficient. The preferred RQE environment rules out satellite-specific quenching processes for most. Under the assumption that most RQEs were quenched by...

  20. Wind from black hole accretion disk as the driver of a molecular outflow in a galaxy

    CERN Document Server

    Tombesi, F; Veilleux, S; Reeves, J N; Gonzalez-Alfonso, E; Reynolds, C S

    2015-01-01

    Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. Recent observations of large-scale molecular outflows in ultra-luminous infrared galaxies (ULIRGs) have provided the evidence to support these studies, as they directly trace the gas out of which stars form. Theoretical models suggest an origin of these outflows as energy-conserving flows driven by fast AGN accretion disk winds. Previous claims of a connection between large-scale molecular outflows and AGN activity in ULIRGs were incomplete because they were lacking the detection of the putative inner wind. Conversely, studies of powerful AGN accretion disk winds to date have focused only on X-ray observations of local Seyferts and a few higher redshift quasars. Here we show the clear detection of a powerful AGN accretion disk wind with a mildly relativistic ...

  1. The flaring HI disk of the nearby spiral galaxy NGC 2683

    CERN Document Server

    Vollmer, B; Ibata, R

    2015-01-01

    New deep VLA D array HI observations of the highly inclined nearby spiral galaxy NGC 2683 are presented. Archival C array data were processed and added to the new observations. To investigate the 3D structure of the atomic gas disk, we made different 3D models for which we produced model HI data cubes. The main ingredients of our best-fit model are (i) a thin disk inclined by 80 degrees; (ii) a crude approximation of a spiral and/or bar structure by an elliptical surface density distribution of the gas disk; (iii) a slight warp in inclination; (iv) an exponential flare; and (v) a low surface-density gas ring. The slope of NGC 2683's flare is comparable, but somewhat steeper than those of other spiral galaxies. NGC 2683's maximum height of the flare is also comparable to those of other galaxies. On the other hand, a saturation of the flare is only observed in NGC 2683. Based on the comparison between the high resolution model and observations, we exclude the existence of an extended atomic gas halo around the ...

  2. The dark matter halo shape of edge-on disk galaxies - IV. UGC 7321

    CERN Document Server

    O'Brien, J C; van der Kruit, P C

    2010-01-01

    This is the fourth paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. We observed for this purpose the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. We have analysed the HI channel maps to accurately measure all four functions that describe the HI kinematics and 3D distribution: the radial HI surface density, the HI vertical thickness, the rotation curve and the HI velocity dispersion. In this paper we analyse these data for the edge-on galaxy UGC7321. We measured the stellar mass distribution ($M=3\\times10^8$ \\msun with $M/L_R\\lesim0.2$), finding that the vertical force of the gas disk dominates the stellar disk at all radii. We find that the vertical force puts a much stronger constraint on the stellar mass-to-light ratio than rotation curve decomposition. Fitting of the vertical force field derived from the f...

  3. A spectroscopic study of blue supergiant stars in the Sculptor galaxy NGC 55: chemical evolution and distance

    CERN Document Server

    Kudritzki, Rolf; Castro, Norberto; Ho, I-Ting; Bresolin, Fabio; Gieren, Wolfgang; Pietrzynski, Grzegorz; Przybilla, Norbert

    2016-01-01

    Low resolution (4.5 to 5 Angstroem) spectra of 58 blue supergiant stars distributed over the disk of the Magellanic spiral galaxy NGC 55 in the Sculptor group are analyzed by means of non-LTE techniques to determine stellar temperatures, gravities and metallicities (from iron peak and alpha-elements). A metallicity gradient of -0.22 +/- 0.06$ dex/R_25 is detected. The central metallicity on a logarithmic scale relative to the Sun is [Z] = -0.37 +\\- 0.03. A chemical evolution model using the observed distribution of stellar and interstellar medium gas mass column densities reproduces the observed metallicity distribution well and reveals a recent history of strong galactic mass accretion and wind outflows with accretion and mass-loss rates of the order of the star formation rate. There is an indication of spatial inhomogeneity in metallicity. In addition, the relatively high central metallicity of the disk confirms that two extra-planar metal poor HII regions detected in previous work 1.13 to 2.22 kpc above th...

  4. Cloud and Star Formation in Disk Galaxy Models with Feedback

    CERN Document Server

    Shetty, Rahul

    2008-01-01

    We include feedback in global hydrodynamic simulations in order to study the star formation properties, and gas structure and dynamics, in models of galactic disks. We extend previous models by implementing feedback in gravitationally bound clouds: momentum is injected at a rate proportional to the star formation rate. This mechanical energy disperses cloud gas back into the surrounding ISM, truncating star formation in a given cloud, and raising the overall level of ambient turbulence. Propagating star formation can however occur as expanding shells collide, enhancing the density and triggering new cloud and star formation. By controlling the momentum injection per massive star and the specific star formation rate in dense gas, we find that the negative effects of high turbulence outweigh the positive ones, and in net feedback reduces the fraction of dense gas and thus the overall star formation rate. The properties of the large clouds that form are not, however, very sensitive to feedback, with cutoff masse...

  5. Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions

    CERN Document Server

    Tan, J C

    1999-01-01

    We invoke star formation triggered by cloud-cloud collisions to explain global star formation rates of disk galaxies and circumnuclear starbursts. Previous theories based on the growth rate of gravitational perturbations ignore the dynamically important presence of magnetic fields. Theories based on triggering by spiral density waves fail to explain star formation in systems without such waves. Furthermore, observations suggest gas and stellar disk instabilities are decoupled. Following the numerical work of Gammie, Jog & Ostriker (1991), the cloud collision rate is set by the shear velocity of encounters with initial impact parameters of a few tidal radii, due to differential rotation in the disk. This enhances the collision rate above that calculated from simply considering the random velocities of clouds. We predict Sigma_{SFR}(R) is proportional to Sigma_{gas} Omega (1 - 0.7 beta). In the case of constant circular velocity (beta = 0), this is in agreement with recent observations (Kennicutt 1998). We ...

  6. GREEN GALAXIES IN THE COSMOS FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zhizheng; Kong, Xu; Fan, Lulu, E-mail: panzz@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Center of Astrophysics, University of Science and Technology of China, Hefei 230026 (China)

    2013-10-10

    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV–r {sup +} color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M{sub 20} planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, based on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ{sub 10}) distributions at z > 0.7. At z < 0.7, the fractions of M{sub *} < 10{sup 10.0} M{sub ☉} green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M{sub *} < 10{sup 10.0} M{sub ☉} blue galaxies into red galaxies, especially at z < 0.5.

  7. The Link Between Light and Mass in Late-type Spiral Galaxy Disks

    CERN Document Server

    Swaters, Robert A; Martinsson, Thomas P K; Westfall, Kyle B; Andersen, David R; Verheijen, Marc A W

    2014-01-01

    We present the correlation between the extrapolated central disk surface brightness (mu) and extrapolated central surface mass density (Sigma) for galaxies in the DiskMass sample. This mu-Sigma-relation has a small scatter of 30% at the high-surface-brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the mu-Sigma-relation, which we attribute to their higher dark matter content. After correcting for the dark matter, as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear mu-Sigma-relation. The resulting scatter about the corrected mu-Sigma-relation is 25% at the HSB end, and about 50% at the LSB end. The intrinsic scatter in the mu-Sigma-relation is estimated to be 10% to 20%. Thus, if the surface brightness is known, the stellar surface mass density is known to within 10-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average (M_L)_K is 0.24 Msun/Lsun, with an intrinsic...

  8. Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components

    CERN Document Server

    Pierini, D; Witt, A N; Madsen, G J

    2004-01-01

    We present results of new Monte Carlo calculations made with the DIRTY code of radiative transfer of stellar and scattered radiation for a dusty giant late-type galaxy like the Milky Way, which illustrate the effect of the attenuation of stellar light by internal dust on the integrated photometry of the individual bulge and disk components. Here we focus on the behavior of the attenuation function, the color excess, and the fraction of light scattered or directly transmitted towards the outside observer as a function of the total amount of dust and the inclination of the galaxy, and the structure of the dusty interstellar medium (ISM) of the disk. We confirm that dust attenuation produces qualitatively and quantitatively different effects on the integrated photometry of bulge and disk, whatever the wavelength. In addition, we find that the structure of the dusty ISM affects more sensitively the observed magnitudes than the observed colors of both bulge and disk. Finally, we show that the contribution of the s...

  9. Star Formation and Metallicity Gradients in Semi-analytic Models of Disk Galaxy Formation

    CERN Document Server

    Fu, Jian; Huang, Meiling; Yates, Robert M; Moran, Sean; Heckman, Timothy M; Davé, Romeel; Guo, Qi

    2013-01-01

    We updated our radially-resolved SAMs of galaxy formation to track the radial distribution of stars, metals, atomic and molecular gas in galactic disks. The models are run on both MS and MS II using the recipes outlined in Fu et al. (2010) and Guo et al. (2011), with 3 main changes: (1) We adopt a simple star formation law where \\Sigma_SFR \\propto \\Sigma_H2. (2) We inject the heavy elements produced by SNe directly into the halo, instead of first mixing them with the disk cold gas. (3) We include radial gas inflows in disks using a model of the form v_inflow=alpha r. The average \\Sigma_H2 profiles in L_* galaxies strongly constrains the inflow velocities, favoring models where v_inflow ~ 7 km/s at r=10 kpc. The radial inflow model has little influence on the gas and stellar metallicity gradients in the outer disks. Gas metallicity gradients are affected much more strongly by the fraction of metals that are directly injected into the halo gas, rather than mixed with the interstellar cold gas. Metals ejected ou...

  10. Circumnuclear Molecular Gas in Megamaser Disk Galaxies NGC 4388 and NGC 1194

    CERN Document Server

    Greene, Jenny E; Lyubenova, Mariya; Walsh, Jonelle; van de Ven, Glenn; Laesker, Ronald

    2014-01-01

    We explore the warm molecular and ionized gas in the centers of two megamaser disk galaxies using K-band spectroscopy. Our ultimate goal is to determine how gas is funneled onto the accretion disk, here traced by megamaser spots on sub-pc scales. We present NIR IFU data with a resolution of ~50 pc for two galaxies: NGC 4388 with VLT/SINFONI and NGC 1194 with Keck/OSIRIS+AO. The high spatial resolution and rich spectral diagnostics allow us to study both the stellar and gas kinematics as well as gas excitation on scales only an order of magnitude larger than the maser disk. We find a drop in the stellar velocity dispersion in the inner ~100 pc of NGC 4388, a common signature of a dynamically cold central component seen in many active nuclei. We also see evidence for non-circular gas motions in the molecular hydrogen on similar scales, with the gas kinematics on 100-pc scales aligned with the megamaser disk. In contrast, the high ionization lines and Br-gamma trace outflow along the 100 pc-scale jet. In NGC 119...

  11. Cannibals in the thick disk: the young $\\alpha-$rich stars as evolved blue stragglers

    CERN Document Server

    Jofre, P; Izzard, R G; Van Eck, S; Hawkins, K; Jorissen, A; Gilmore, G; Paladini, C

    2016-01-01

    Spectro-seismic measurements of red giant stars enabled the recent discovery of giant stars in the thick disk that are more massive than 1.4 M_sun (Martig et al 2015, Chiappini et al 2015). While it has been claimed that most of these stars are younger than the rest of the typical thick disk stars, we show evidence that they might be products of mass transfer in binary evolution, notably evolved blue stragglers. We took new measurements of the radial velocities in a sample of 26 stars from APOKASC, including 13 of the "young" stars of Martig et al (2015) and 13 "old" stars with similar stellar parameters but with masses below 1 M_sun and found that some stars are in binary systems, contrary to what has been claimed before. Furthermore, with a population synthesis of only low-mass stars but including binary evolution and mass transfer, we can reproduce the masses and the [C/N] ratios of the 26 stars. Our study shows how asteroseismology of solar-type red giants provides us with a unique opportunity to study th...

  12. Semi-analytic models for HI gas in disk and local dwarf galaxies

    Science.gov (United States)

    Fu, Jian

    2015-08-01

    We construct the radially-resolved semi-analytic models of galaxy formation based on the L-Galaxies model framework, which include both atomic and molecular gas phase in ISM. The models adopt the ΛCDM cosmology simulation Millennium, Millennium II and Aquarius. Our models can reproduce varies properties of HI gas in nearby galaxies, e.g. the HI mass function, the HI-to-star ratio vs stellar mass and stellar surface density, universal HI radial surface density profile in outer disks etc. We can also give some physical origins of HI size mass relation in many observations.Based on our model results for local dwarf galaxies, we show that the "missing satellite problem" also exists in the HI component, i.e., the models over predict dwarf galaxies with low HI mass. That is a shortcoming of current ΛCDM cosmology framework. Future survey for HI gas in dwarf galaxies (e.g. SKA or FAST) in local group can help to verify the correctness of cold dark matter.

  13. 13CO/C18O Gradients across the Disks of Nearby Spiral Galaxies

    Science.gov (United States)

    Jiménez-Donaire, María J.; Cormier, Diane; Bigiel, Frank; Leroy, Adam K.; Gallagher, Molly; Krumholz, Mark R.; Usero, Antonio; Hughes, Annie; Kramer, Carsten; Meier, David; Murphy, Eric; Pety, Jérôme; Schinnerer, Eva; Schruba, Andreas; Schuster, Karl; Sliwa, Kazimierz; Tomicic, Neven

    2017-02-01

    We use the IRAM Large Program EMPIRE and new high-resolution ALMA data to measure 13CO(1-0)/C18O(1-0) intensity ratios across nine nearby spiral galaxies. These isotopologues of 12CO are typically optically thin across most of the area in galaxy disks, and this ratio allows us to gauge their relative abundance due to chemistry or stellar nucleosynthesis effects. Resolved 13CO/C18O gradients across normal galaxies have been rare due to the faintness of these lines. We find a mean 13CO/C18O ratio of 6.0 ± 0.9 for the central regions of our galaxies. This agrees well with results in the Milky Way, but differs from results for starburst galaxies (3.4 ± 0.9) and ultraluminous infrared galaxies (1.1 ± 0.4). In our sample, the 13CO/C18O ratio consistently increases with increasing galactocentric radius and decreases with increasing star formation rate surface density. These trends could be explained if the isotopic abundances are altered by fractionation; the sense of the trends also agrees with those expected for carbon and oxygen isotopic abundance variations due to selective enrichment by massive stars.

  14. Shape Evolution of Massive Early-Type Galaxies: Confirmation of Increased Disk Prevalence at z>1

    CERN Document Server

    Chang, Yu-Yen; Rix, Hans-Walter; Wuyts, Stijn; Zibetti, Stefano; Ramkumar, Balasubramanian; Holden, Bradford P

    2012-01-01

    We use high-resolution K-band VLT/HAWK-I imaging over 0.25 square degrees to study the structural evolution of massive early-type galaxies since z~1. Mass-selected samples, complete down to log(M/M_sun)~10.7 such that `typical' L* galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separated the samples into different redshift slices and classify them as late- or early-type galaxies on the basis of their specific star-formation rate. Axis-ratio measurements for the ~400 early-type galaxies in the redshift range 0.61 are, on average, flatter than at z11.3) are the roundest, with a pronounced lack among them of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs merging is required for early-type galaxies to grow beyond log(M/M_sun)~11.3, and all early types over time gradually and partially loose their disk-like characteristics.

  15. The Flying Spaghetti Monster: Impact of magnetic fields on ram pressure stripping in disk galaxies

    CERN Document Server

    Ruszkowski, M; Lee, D; Shin, M -S

    2012-01-01

    Ram pressure stripping can remove significant amounts of gas from galaxies in clusters, and thus has a large impact on the evolution of cluster galaxies. Recent observations have shown that key properties of ram-pressure stripped tails of galaxies, such as their width and structure, are in conflict with predictions by simulations. To increase the realism of existing simulations, we simulated for the first time a disk galaxy exposed face-on to a uniformly magnetized wind including radiative cooling and self-gravity of the gas. We find that magnetic fields have a strong effect on the morphology of the gas in the tail of the galaxy. While in the purely hydrodynamical case the tail is very clumpy, the MHD case shows very filamentary structures in the tail. The filaments can be strongly supported by magnetic pressure and, wherever this is the case, the magnetic fields vectors tend to be aligned with the filaments. Interestingly, we observe the formation of two dominant magnetized density tails behind the galaxy re...

  16. Kinematic classifications of local interacting galaxies: implications for the merger/disk classifications at high-z

    CERN Document Server

    Hung, Chao-Ling; Yuan, Tiantian; Larson, Kirsten L; Casey, Caitlin M; Smith, Howard A; Sanders, D B; Kewley, Lisa J; Hayward, Christopher C

    2015-01-01

    The classification of galaxy mergers and isolated disks is key for understanding the relative importance of galaxy interactions and secular evolution during the assembly of galaxies. The kinematic properties of galaxies as traced by emission lines have been used to suggest the existence of a significant population of high-z star-forming galaxies consistent with isolated rotating disks. However, recent studies have cautioned that post-coalescence mergers may also display disk-like kinematics. To further investigate the robustness of merger/disk classifications based on kinematic properties, we carry out a systematic classification of 24 local (U)LIRGs spanning a range of galaxy morphologies: from isolated spiral galaxies, ongoing interacting systems, to fully merged remnants. We artificially redshift the WiFeS observations of these local (U)LIRGs to z=1.5 to make a realistic comparison with observations at high-z, and also to ensure that all galaxies have the same spatial sampling of ~900 pc. Using both kineme...

  17. Kinematic Constraints on Evolutionary Scenarios for Blue Compact Dwarf Galaxies I. Neutral Gas Dynamics

    CERN Document Server

    Van Zee, L; Skillman, E D; Zee, Liese van; Salzer, John J.; Skillman, Evan D.

    2001-01-01

    We present the results of high spatial resolution HI synthesis observations of six blue compact dwarf (BCD) galaxies. Optically, the selected galaxies have smooth, symmetric isophotes, and thus are the most likely of the BCD class to fade into an object morphologically similar to a dwarf elliptical when the current starburst ends. The neutral gas in all six galaxies appears to be rotationally supported, however, indicating that true morphological transformation from a BCD to a dE will require significant loss of angular momentum. Based on the observed neutral gas dynamics of these and other BCDs, it is unlikely that present-day BCDs will evolve directly into dwarf ellipticals after a starburst phase. We discuss alternative evolutionary scenarios for BCDs and place them within the larger context of galaxy formation and evolution models.

  18. Evolution in the Disks and Bulges of Group Galaxies since z=0.4

    CERN Document Server

    McGee, Sean L; Henderson, Robert D E; Wilman, David J; Bower, Richard G; Mulchaey, John S; Oemler, Augustus

    2008-01-01

    We present quantitative morphology measurements of a sample of optically selected group galaxies at 0.3 < z < 0.55 using the Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) and the GIM2D surface brightness--fitting software package. The group sample is derived from the Canadian Network for Observational Cosmology Field Redshift survey (CNOC2) and follow-up Magellan spectroscopy. We compare these measurements to a similarly selected group sample from the Millennium Galaxy Catalogue (MGC) at 0.05 < z < 0.12. We find that, at both epochs, the group and field fractional bulge luminosity (B/T) distributions differ significantly, with the dominant difference being a deficit of disk--dominated (B/T < 0.2) galaxies in the group samples. At fixed luminosity, z=0.4 groups have ~ 5.5 +/- 2 % fewer disk--dominated galaxies than the field, while by z=0.1 this difference has increased to ~ 19 +/- 6 %. Despite the morphological evolution we see no evidence that the group environment is actively...

  19. Mass Transport and Turbulence in Gravitationally Unstable Disk Galaxies II: The Effects of Star Formation Feedback

    CERN Document Server

    Goldbaum, Nathan J; Forbes, John C

    2016-01-01

    Self-gravity and stellar feedback are capable of driving turbulence and transporting mass and angular momentum in disk galaxies, but the balance between them is not well understood. In the previous paper in this series, we showed that gravity alone can drive turbulence in galactic disks, regulate their Toomre $Q$ parameters to $\\sim$ 1, and transport mass inwards at a rate sufficient to fuel star formation in the centers of present-day galaxies. In this paper we extend our models to include the effects of star formation feedback. We show that feedback suppresses galaxies' star formation rates by a factor of $\\sim$ 5 and leads to the formation of a multi-phase atomic and molecular ISM. Both the star formation rate and the phase balance produced in our simulations agree well with observations of nearby spirals. After our galaxies reach steady state, we find that the inclusion of feedback actually lowers the gas velocity dispersion slightly compared to the case of pure self-gravity, and also slightly reduces the...

  20. The First Galaxies: Assembly of Disks and Prospects for Direct Detection

    CERN Document Server

    Pawlik, Andreas H; Bromm, Volker

    2010-01-01

    The James Webb Space Telescope (JWST) will enable observations of galaxies at redshifts z > 10 and hence allow to test our current understanding of structure formation at very early times. Previous work has shown that the very first galaxies inside halos with virial temperatures T 10 are probably too faint, by at least one order of magnitude, to be detected even in deep exposures with JWST. The light collected with JWST may therefore be dominated by radiation from galaxies inside ten times more massive halos. We use cosmological zoomed smoothed particle hydrodynamics simulations to investigate the assembly of such galaxies and assess their observability with JWST. We compare two simulations that are identical except for the inclusion of non-equilibrium H/D chemistry and radiative cooling by molecular hydrogen. In both simulations a large fraction of the halo gas settles in two nested, extended gas disks which surround a compact massive gas core. The presence of molecular hydrogen allows the disk gas to reach...

  1. Seeking large-scale magnetic fields in a pure-disk dwarf galaxy NGC 2976

    CERN Document Server

    Drzazga, R T; Heald, G H; Elstner, D; Gallagher, J S

    2016-01-01

    It is still unknown how magnetic field-generation mechanisms could operate in low-mass dwarf galaxies. Here, we present a detailed study of a nearby pure-disk dwarf galaxy NGC 2976. Unlike previously observed dwarf objects, this galaxy possesses a clearly defined disk. For the purpose of our studies, we performed deep multi-frequency polarimetric observations of NGC 2976 with the VLA and Effelsberg radio telescopes. Additionally, we supplement them with re-imaged data from the WSRT-SINGS survey. The magnetic field morphology discovered in NGC 2976 consists of a southern polarized ridge. This structure does not seem to be due to just a pure large-scale dynamo process (possibly cosmic-ray driven) at work in this object, as indicated by the RM data and dynamo number calculations. Instead, the field of NGC 2976 is modified by past gravitational interactions and possibly also by ram pressure inside the M 81 galaxy group environment. The estimates of total (7 muG) and ordered (3 muG) magnetic field strengths, as we...

  2. Ab initio Simulations of a Supernova Driven Galactic Dynamo in an Isolated Disk Galaxy

    CERN Document Server

    Butsky, Iryna; Kim, Ji-hoon; Yang, Hung-I; Abel, Tom

    2016-01-01

    We study the magnetic field evolution of an isolated spiral galaxy, using isolated Milky Way-mass galaxy formation simulations and a novel prescription for magnetohydrodynamic (MHD) supernova feedback. Our main result is that a galactic dynamo can be seeded and driven by supernova explosions, resulting in magnetic fields whose strength and morphology is consistent with observations. In our model, supernovae supply thermal energy, and a low level magnetic field along with their ejecta. The thermal expansion drives turbulence, which serves a dual role by efficiently mixing the magnetic field into the interstellar medium, and amplifying it by means of turbulent dynamo. The computational prescription for MHD supernova feedback has been implemented within the publicly available ENZO code, and is fully described in this paper. This improves upon ENZO's existing modules for hydrodynamic feedback from stars and active galaxies. We find that the field attains $\\mu G$-levels over Gyr-time scales throughout the disk. Th...

  3. NoSOCS in SDSS. V. Red Disc and Blue Bulge Galaxies Across Different Environments

    CERN Document Server

    Lopes, P A A; Ribeiro, A L B; Nascimento, R S; Vajgel, B

    2016-01-01

    We investigated the typical environment and physical properties of "red discs" and "blue bulges", comparing those to the "normal" objects in the blue cloud and red sequence. Our sample is composed of cluster members and field galaxies at $z \\le 0.1$, so that we can assess the impact of the local and global environment. We find that disc galaxies display a strong dependence on environment, becoming redder for higher densities. This effect is more pronounced for objects within the virial radius, being also strong related to the stellar mass. We find that local and global environment affect galaxy properties, but the most effective parameter is stellar mass. We find evidence for a scenario where "blue discs" are transformed into "red discs" as they grow in mass and move to the inner parts of clusters. From the metallicity differences of red and blue discs, and the analysis of their star formation histories, we suggest the quenching process is slow. We estimate a quenching time scale of $\\sim $ 2$-$3 Gyr. We also...

  4. The red extended structure of IC10, the nearest blue compact galaxy

    CERN Document Server

    Gerbrandt, Stephanie A N; Irwin, Mike

    2015-01-01

    The Local Group starburst galaxy IC10 is the closest example of a blue compact galaxy. Here, we use optical gi imaging from CFHT/MegaCam and near infra-red JHK imaging from UKIRT/WFCAM to conduct a comprehensive survey of the structure of IC10. We examine the spatial distribution of its resolved young, intermediate and old stellar populations to large radius and low effective surface brightness levels. Akin to other dwarfs with multiple populations of different ages, stellar populations of decreasing average age are increasingly concentrated in this galaxy. We find that the young, star-bursting population, and the AGB population, are both offset from the geometric center of the older RGB population by a few hundred parsecs, implying that the younger star formation occurred significantly away from the center of the galaxy. The RGB population traces an extended structure that is typical of blue compact galaxies, with an effective radius of ~5.75 arcmins (~1.25 kpc). These measurements show that IC10 is much mor...

  5. The Space Density of Extended Ultraviolet (XUV) Disks in the Local Universe and Implications for Gas Accretion on to Galaxies

    CERN Document Server

    Lemonias, Jenna J; Thilker, David; Wyder, Ted K; Martin, D Christopher; Seibert, Mark; Treyer, Marie A; Bianchi, Luciana; Heckman, Timothy M; Madore, Barry F; Rich, R Michael

    2011-01-01

    We present results of the first unbiased search for extended UV (XUV)-disk galaxies undertaken to determine the space density of such galaxies. Our sample contains 561 local (0.001 1.5 x 10^4 s) and SDSS DR7 footprints. We explore modifications to the standard classification scheme for our sample that includes both disk- and bulge-dominated galaxies. Visual classification of each galaxy in the sample reveals an XUV-disk frequency of up to 20% for the most nearby portion of our sample. On average over the entire sample (out to z=0.05) the frequency ranges from a hard limit of 4% to 14%. The GALEX imaging allows us to detect XUV-disks beyond 100 Mpc. The XUV regions around XUV-disk galaxies are consistently bluer than the main bodies. We find a surprisingly high frequency of XUV emission around luminous red (NUV-r > 5) and green valley (3 1.5-4.2 x 10^-3 Mpc^-3. Using the XUV emission as an indicator of recent gas accretion, we estimate that the cold gas accretion rate onto these galaxies is > 1.7-4.6 x 10^-3...

  6. THE LINK BETWEEN LIGHT AND MASS IN LATE-TYPE SPIRAL GALAXY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Swaters, Robert A. [National Optical Astronomical Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Bershady, Matthew A. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Martinsson, Thomas P. K. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Westfall, Kyle B. [Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Burnaby Road, Portsmouth PO1 3FX (United Kingdom); Andersen, David R. [NRC Herzberg Programs in Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7 (Canada); Verheijen, Marc A. W., E-mail: rob@swaters.net [University of Groningen, Kapteyn Astronomical Institute, Landleven 12, 9747-AD Groningen (Netherlands)

    2014-12-20

    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the μ-Σ relation, which we attribute to their higher dark matter content. After correcting for the dark matter as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear μ-Σ relation. The resulting scatter around the corrected μ-Σ relation is 25% at the HSB end and about 50% at the LSB end. The intrinsic scatter in the μ-Σ relation is estimated to be 10%-20%. Thus, if μ {sub K,} {sub 0} is known, the stellar surface mass density is known to within 10%-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average Υ{sub ∗}{sup K} is 0.24 M {sub ☉}/L {sub ☉}, with an intrinsic scatter around the mean of at most 0.05 M {sub ☉}/L {sub ☉}. This value for Υ{sub ∗}{sup K} is 20% smaller than we found in Martinsson et al., mainly due to the correction for dark matter applied here. This small scatter means that among the galaxies in our sample, variations in scale height, vertical density profile shape, and/or the ratio of vertical over radial velocity dispersion must be small.

  7. The Link between Light and Mass in Late-type Spiral Galaxy Disks

    Science.gov (United States)

    Swaters, Robert A.; Bershady, Matthew A.; Martinsson, Thomas P. K.; Westfall, Kyle B.; Andersen, David R.; Verheijen, Marc A. W.

    2014-12-01

    We present the correlation between the extrapolated central disk surface brightness (μ) and extrapolated central surface mass density (Σ) for galaxies in the DiskMass sample. This μ-Σ relation has a small scatter of 30% at the high surface brightness (HSB) end. At the low surface brightness (LSB) end, galaxies fall above the μ-Σ relation, which we attribute to their higher dark matter content. After correcting for the dark matter as well as for the contribution of gas and the effects of radial gradients in the disk, the LSB end falls back on the linear μ-Σ relation. The resulting scatter around the corrected μ-Σ relation is 25% at the HSB end and about 50% at the LSB end. The intrinsic scatter in the μ-Σ relation is estimated to be 10%-20%. Thus, if μ K, 0 is known, the stellar surface mass density is known to within 10%-20% (random error). Assuming disks have an exponential vertical distribution of mass, the average \\Upsilon _\\ast ^K is 0.24 M ⊙/L ⊙, with an intrinsic scatter around the mean of at most 0.05 M ⊙/L ⊙. This value for \\Upsilon _\\ast ^K is 20% smaller than we found in Martinsson et al., mainly due to the correction for dark matter applied here. This small scatter means that among the galaxies in our sample, variations in scale height, vertical density profile shape, and/or the ratio of vertical over radial velocity dispersion must be small.

  8. The DEEP2 Galaxy Redshift Survey: The evolution of the blue fraction in groups and the field

    CERN Document Server

    Gerke, B F; Faber, S M; Cooper, M C; Croton, D J; Davis, M; Willmer, C N A; Yan, R; Coil, A L; Guhathakurta, P; Koo, D C; Weiner, B J; Gerke, Brian F.; Newman, Jeffrey A.; Cooper, Michael C.; Croton, Darren J.; Davis, Marc; Willmer, Christopher N. A.; Yan, Renbin; Coil, Alison L.; Guhathakurta, Puragra; Koo, David C.; Weiner, Benjamin J.

    2006-01-01

    We explore the behavior of the blue galaxy fraction over the redshift range 0.75 <= z <= 1.3 in the DEEP2 Survey, both for field galaxies and for galaxies in groups. The primary aim is to determine the role that groups play in driving the evolution of galaxy colour at high z. The colour segregation observed between local group and field samples is already in place at z ~ 1: DEEP2 groups have a significantly lower blue fraction than the field. At fixed z, there is also a correlation between blue fraction and galaxy magnitude, such that brighter galaxies are more likely to be red, both in groups and in the field. In addition, there is a negative correlation between blue fraction and group richness. In terms of evolution, the blue fraction in groups and the field remains roughly constant from z=0.75 to z ~ 1, but beyond this redshift the blue fraction in groups rises rapidly with z, and the group and field blue fractions become indistinguishable at z ~ 1.3. Careful tests indicate that this effect does not ...

  9. Chemo-Dynamical Evolution of Disk Galaxies, Smoothed Particles Hydrodynamics Approach

    Science.gov (United States)

    Berczik, P.

    In this paper I present, the new Chemo-Dynamical code, incorporated to the standard Smoothed Particle Hydrodynamics (CD-SPH). This code used to modelling the complex evolution of disk galaxy systems. The more detailed description of SPH code and the Star Formation (SF) and Super Novae (SN) algorithms you can find in our earlier work Berczik P. & Kravchuk S.G., 1996, ApSpSci, 245, 27. The galaxy presented via tree component system. The Dark Matter Halo described as an external gravitational potential with distribution of Dark Matter density (Burkert A. 1995, ApJ, 447, L25): ρDM (r) = frac ρ0 (1 + r / r0) cdot (1 + r / r0)2. The total mass of Dark Matter Halo is 1012 Modot. The second component is a hot coronal gas, with Thot ~106 K. This component presented as a uniformly distributed SPH gas with initial solid body rotation and with additisional random velocity component Δ V ~100 km/sec. The total mass of this component is 5 cdot 1010 Modot. The last component is a cold gas (Tcold ~104 K). This component presented also as a uniformly distributed SPH gas with initial solid body rotation and with additional random velocity component Δ V ~10 km/sec. The total mass of this component also is 5 cdot 1010 Modot. In the paper presented a more complex and may be more realistic incorporation of SF & SN in the SPH code. The presented calculation is clearly show, what the some interestiong and important properties of isolated disk galaxies we can explain using this simple, tree component "collapsing" model. In the frame of this approach we are able to reproduce the presently observed kinematics of star and gaseous components as well as their distributions and heavy element abundances. The developed model provide the realystic description of dynamics and chemical evolution of typical disk galaxies over the Hubble timescale.

  10. Mass Distribution in Rotating Thin-Disk Galaxies According to Newtonian Dynamics

    Directory of Open Access Journals (Sweden)

    James Q. Feng

    2014-04-01

    Full Text Available An accurate computational method is presented for determining the mass distribution in a mature spiral galaxy from a given rotation curve by applying Newtonian dynamics for an axisymmetrically rotating thin disk of finite size with or without a central spherical bulge. The governing integral equation for mass distribution is transformed via a boundary-element method into a linear algebra matrix equation that can be solved numerically for rotation curves with a wide range of shapes. To illustrate the effectiveness of this computational method, mass distributions in several mature spiral galaxies are determined from their measured rotation curves. All the surface mass density profiles predicted by our model exhibit approximately a common exponential law of decay, quantitatively consistent with the observed surface brightness distributions. When a central spherical bulge is present, the mass distribution in the galaxy is altered in such a way that the periphery mass density is reduced, while more mass appears toward the galactic center. By extending the computational domain beyond the galactic edge, we can determine the rotation velocity outside the cut-off radius, which appears to continuously decrease and to gradually approach the Keplerian rotation velocity out over twice the cut-off radius. An examination of circular orbit stability suggests that galaxies with flat or rising rotation velocities are more stable than those with declining rotation velocities especially in the region near the galactic edge. Our results demonstrate the fact that Newtonian dynamics can be adequate for describing the observed rotation behavior of mature spiral galaxies.

  11. Collisions and Mergers of Disk Galaxies Hydrodynamics of Star Forming Gas

    CERN Document Server

    Lamb, S A; Hearn, Nathan C.

    2003-01-01

    We summarize the results of numerical simulations of colliding gas-rich disk galaxies in which the impact velocity is set parallel to the spin axes of the two galaxies. The effects of varying the impact speed are studied with particular attention to the resulting gaseous structures and shockwave patterns, and the time needed to produce these structures. The simulations employ an N-body treatment of the stars and dark matter, together with an SPH treatment of the gas, in which all components of the models are gravitationally active. The results indicate that for such impact geometries, collisions can lead to the very rapid formation of a central, rapidly rotating, dense gas disk, and that in all cases extensive star formation is predicted by the very high gas densities and prevalence of shocks, both in the nucleus and out in the galactic disks. As the dense nucleus is forming, gas and stars are dispersed over very large volumes, and only fall back towards the nucleus over long times. In the case of low impact ...

  12. Disks controlling chaos in a 3D dynamical model for elliptical galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2011-01-01

    A 3D dynamical model with a quasi-homogeneous core and a disk component is used for the chaos control in the central parts of elliptical galaxy. Numerical experiments in the 2D system show a very complicated phase plane with a large chaotic sea, considerable sticky layers and a large number of islands, produced by secondary resonances. When the mass of the disk increases, the chaotic regions decrease gradually, and, finally, a new phase plane with only regular orbits appears. This evolution indicates that disks in elliptical galaxies can act as the chaos controllers. Starting from the results obtained in the 2D system, we locate the regions in the phase space of the 3D system, producing regular and chaotic orbits. For this we introduce and use a new dynamical parameter, the S(w) spectrum, which proves to be useful as a fast indicator and allows us to distinguish the regular motion from chaos in the 3D potentials. Other methods for detecting chaos are also discussed.

  13. Formation and evolution of molecular hydrogen in disk galaxies with different masses and Hubble types

    CERN Document Server

    Bekki, Kenji

    2014-01-01

    We investigate the physical properties of molecular hydrogen (H2) in isolated and interacting disk galaxies with different masses and Hubble types by using chemodynamical simulations with H2 formation on dust grains and dust growth and destruction in interstellar medium (ISM). We particularly focus on the dependences of H2 gas mass fractions (f_H2), spatial distributions of HI and H2, and local H2-scaling relations on initial halo masses (M_h), baryonic fractions (f_bary), gas mass fractions (f_g), and Hubble types. The principal results are as follows. The final f_H2 can be larger in disk galaxies with higher M_h, f_bary, and f_g. Some low-mass disk models with M_h smaller than 10^10 M_sun show extremely low f_H2 and thus no/little star formation, even if initial f_g is quite large (>0.9). Big galactic bulges can severely suppress the formation of H2 from HI on dust grains whereas strong stellar bars can not only enhance f_H2 but also be responsible for the formation of H2-dominated central rings. The projec...

  14. Growth and Destruction of Disks: Combined H I and H II View

    NARCIS (Netherlands)

    Bershady, Matthew; Verheijen, Marc; Crawford, Steven

    2008-01-01

    How large disk galaxies have evolved in, and out of, the blue cloud of actively star-forming galaxies as a function of environment and time is an outstanding question. Some of the largest disks become systems like M31, M33 and the Milky Way today. In denser environments, it appears they transform on

  15. A characteristic oxygen abundance gradient in galaxy disks unveiled with CALIFA

    CERN Document Server

    Sanchez, S F; Iglesias-Paramo, J; Molla, M; Barrera-Ballesteros, J; Marino, R A; Perez, E; Sanchez-Blazquez, P; Delgado, R Gonzalez; Fernandes, R Cid; de Lorenzo-Caceres, A; Mendez-Abreu, J; Galbany, L; Falcon-Barroso, J; Miralles-Caballero, D; Husemann, B; Garcia-Benito, R; Mast, D; Walcher, C J; de Paz, A Gil; Garcia-Lorenzo, B; Jungwiert, B; Vilchez, J M; Jilkova, Lucie; Lyubenova, M; Cortijo-Ferrero, C; Diaz, A I; Wisotzki, L; Marquez, I; Bland-Hawthorn, J; Ellis, S; van de Ven, G; Jahnke, K; Papaderos, P; Gomes, J M; Mendoza, M A; Lopez-Sanchez, Á R

    2013-01-01

    We present the largest and most homogeneous catalog of HII regions and associations compiled so far. The catalog comprises more than 7000 ionized regions, extracted from 306 galaxies observed by the CALIFA survey. We describe the procedures used to detect, select, and analyse the spectroscopic properties of these ionized regions. In the current study we focus on the characterization of the radial gradient of the oxygen abundance in the ionized gas, based on the study of the deprojected distribution of HII regions. We found that all galaxies without clear evidence of an interaction present a common gradient in the oxygen abundance, with a characteristic slope of alpha = -0.1 dex/re between 0.3 and 2 disk effective radii, and a scatter compatible with random fluctuations around this value, when the gradient is normalized to the disk effective radius. The slope is independent of morphology, incidence of bars, absolute magnitude or mass. Only those galaxies with evidence of interactions and/or clear merging syste...

  16. The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts

    OpenAIRE

    Mandelbaum, Rachel; Blake, Chris; Bridle, Sarah; Abdalla, Filipe B.; Brough, Sarah; Colless, Matthew; Couch, Warrick; Croom, Scott; Davis, Tamara; Drinkwater, Michael J.; Forster, Karl; Glazebrook, Karl; Jelliffe, Ben; Jurek, Russell J; Li, I-hui

    2009-01-01

    Correlations between the intrinsic shapes of galaxy pairs, and between the intrinsic shapes of galaxies and the large-scale density field, may be induced by tidal fields. These correlations, which have been detected at low redshifts (z < 0.35) for bright red galaxies in the Sloan Digital Sky Survey (SDSS), and for which upper limits exist for blue galaxies at z ~ 0.1, provide a window into galaxy formation and evolution, and are also an important contaminant for current and future weak lensin...

  17. Statistical analysis of galaxy surveys - III: The non-linear clustering of red and blue galaxies in the 2dFGRS

    CERN Document Server

    Croton, D J; Gaztañaga, E; Baugh, C M; Croton, Darren J.; Norberg, Peder; Gaztanaga, Enrique; Baugh, Carlton M.

    2006-01-01

    We present measurements of the higher-order clustering of red and blue galaxies as a function of scale and luminosity made from the two-degree field galaxy redshift survey (2dFGRS). We use a counts-in-cells analysis to estimate the volume averaged correlation functions, xi_p, as a function of scale up to order p=5, and also the reduced void probability function. Hierarchical amplitudes are constructed using the estimates of the correlation functions: S_p=(xi_p/xi_2)^(p-1). We find that: 1) Red galaxies display stronger clustering than blue galaxies at all orders measured. 2) Red galaxies show values of S_p that are strongly dependent on luminosity, whereas blue galaxies show no segregation in S_p within the errors; this is remarkable given the segregation in the variance. 3) The linear relative bias shows the opposite trend to the hierarchical amplitudes, with little segregation for the red sequence and some segregation for the blue. 4) Faint red galaxies deviate significantly from the "universal" negative bi...

  18. The AGORA High-resolution Galaxy Simulations Comparison Project. II. Isolated Disk Test

    Science.gov (United States)

    Kim, Ji-hoon; Agertz, Oscar; Teyssier, Romain; Butler, Michael J.; Ceverino, Daniel; Choi, Jun-Hwan; Feldmann, Robert; Keller, Ben W.; Lupi, Alessandro; Quinn, Thomas; Revaz, Yves; Wallace, Spencer; Gnedin, Nickolay Y.; Leitner, Samuel N.; Shen, Sijing; Smith, Britton D.; Thompson, Robert; Turk, Matthew J.; Abel, Tom; Arraki, Kenza S.; Benincasa, Samantha M.; Chakrabarti, Sukanya; DeGraf, Colin; Dekel, Avishai; Goldbaum, Nathan J.; Hopkins, Philip F.; Hummels, Cameron B.; Klypin, Anatoly; Li, Hui; Madau, Piero; Mandelker, Nir; Mayer, Lucio; Nagamine, Kentaro; Nickerson, Sarah; O'Shea, Brian W.; Primack, Joel R.; Roca-Fàbrega, Santi; Semenov, Vadim; Shimizu, Ikkoh; Simpson, Christine M.; Todoroki, Keita; Wadsley, James W.; Wise, John H.; AGORA Collaboration

    2016-12-01

    Using an isolated Milky Way-mass galaxy simulation, we compare results from nine state-of-the-art gravito-hydrodynamics codes widely used in the numerical community. We utilize the infrastructure we have built for the AGORA High-resolution Galaxy Simulations Comparison Project. This includes the common disk initial conditions, common physics models (e.g., radiative cooling and UV background by the standardized package Grackle) and common analysis toolkit yt, all of which are publicly available. Subgrid physics models such as Jeans pressure floor, star formation, supernova feedback energy, and metal production are carefully constrained across code platforms. With numerical accuracy that resolves the disk scale height, we find that the codes overall agree well with one another in many dimensions including: gas and stellar surface densities, rotation curves, velocity dispersions, density and temperature distribution functions, disk vertical heights, stellar clumps, star formation rates, and Kennicutt-Schmidt relations. Quantities such as velocity dispersions are very robust (agreement within a few tens of percent at all radii) while measures like newly formed stellar clump mass functions show more significant variation (difference by up to a factor of ˜3). Systematic differences exist, for example, between mesh-based and particle-based codes in the low-density region, and between more diffusive and less diffusive schemes in the high-density tail of the density distribution. Yet intrinsic code differences are generally small compared to the variations in numerical implementations of the common subgrid physics such as supernova feedback. Our experiment reassures that, if adequately designed in accordance with our proposed common parameters, results of a modern high-resolution galaxy formation simulation are more sensitive to input physics than to intrinsic differences in numerical schemes.

  19. The Escape of Ionizing Photons from OB Associations in Disk Galaxies Radiation Transfer Through Superbubbles

    CERN Document Server

    Dove, J B; Ferrara, A; Dove, James B.; Ferrara, Andrea

    1999-01-01

    By solving the time-dependent radiation transfer problem of stellar radiation through evolving superbubbles within a smoothly varying H I distribution, we have estimated the fraction of ionizing photons emitted by OB associations that escapes the H I disk of our Galaxy. We considered a coeval star-formation history and a Gaussian star-formation history with a time spread sigma_t = 2 Myr. We find that the shells of the expanding superbubbles quickly trap or attenuate the ionizing flux, such that most of the escaping radiation escapes shortly after the formation of the superbubble. Superbubbles of large associations can blowout of the H I disk and form dynamic chimneys, which allow the ionizing radiation directly to escape the H I disk. However, blowout occurs when the ionizing photon luminosity has dropped well below the association's maximum luminosity. For the coeval star-formation history, the fraction of photons that escape each side of the disk in the solar vicinity is f_esc approx 6% (the total fraction ...

  20. What Kinds of Accretion Disks Are There in the Nuclei of Radio Galaxies?

    CERN Document Server

    Kaburaki, Osamu; Tamura, Naoya; Wajima, Kiyoaki

    2010-01-01

    It seems to be a widely accepted opinion that the types of accretion disks (or flows) generally realized in the nuclei of radio galaxies and in further lower mass-accretion rate nuclei are inner, hot, optically thin, radiatively inefficient accretion flows (RIAFs) surrounded by outer, cool, optically thick, standard type accretion disks. However, observational evidence for the existence of such outer cool disks in these nuclei is rather poor. Instead, recent observations sometimes suggest the existence of inner cool disks of non-standard type, which develop in the region very close to their central black holes. Taking NGC 4261 as a typical example of such light eating nuclei, for which both flux data ranging from radio to X-ray and data for the counterjet occultation are available, we examine the plausibility of such a picture for the accretion states as mentioned above, based on model predictions. It is shown that the explanation of the gap seen in the counterjet emission in terms of the free-free absorption...

  1. The ACS Nearby Galaxy Survey Treasury XI. The Remarkably Undisturbed NGC 2403 Disk

    CERN Document Server

    Williams, Benjamin F; Stilp, Adrienne; Dolphin, Andrew; Skillman, Evan D; Radburn-Smith, David

    2013-01-01

    We present detailed analysis of color-magnitude diagrams of NGC2403, obtained from a deep (m<28) Hubble Space Telescope (HST) Wide Field Planetary Camera 2 observation of the outer disk of NGC2403, supplemented by several shallow (m<26) HST Advanced Camera for Surveys fields. We derive the spatially resolved star formation history of NGC2403 out to 11 disk scale lengths. In the inner portions of the galaxy, we compare the recent star formation rates (SFRs) we derive from the resolved stars with those measured using GALEX FUV + Spitzer 24-micron fluxes, finding excellent agreement between the methods. Our measurements also show that the radial gradient in recent SFR mirror s the disk exponential profile to 11 scale lengths with no break, extending to SFR densities a factor of 100 lower than those that can be measured with GALEX and Spitzer (2x10^{-6} M_{\\sun} yr^{-1} kpc^{-2}). Furthermore, we find that the cumulative stellar mass of the disk was formed at similar times at all radii. We compare these cha...

  2. Supernova-driven Turbulence and Magnetic Field Amplification in Disk Galaxies

    CERN Document Server

    Gressel, Oliver

    2010-01-01

    Supernovae are known to be the dominant energy source for driving turbulence in the interstellar medium. Yet, their effect on magnetic field amplification in spiral galaxies is still poorly understood. Analytical models based on the uncorrelated-ensemble approach predicted that any created field will be expelled from the disk before a significant amplification can occur. By means of direct simulations of supernova-driven turbulence, we demonstrate that this is not the case. Accounting for vertical stratification and galactic differential rotation, we find an exponential amplification of the mean field on timescales of 100Myr. The self-consistent numerical verification of such a "fast dynamo" is highly beneficial in explaining the observed strong magnetic fields in young galaxies. We, furthermore, highlight the importance of rotation in the generation of helicity by showing that a similar mechanism based on Cartesian shear does not lead to a sustained amplification of the mean magnetic field. This finding impr...

  3. Computer experiments on the effect of retrograde stars in disk galaxies

    Science.gov (United States)

    Zang, T. A.; Hohl, F.

    1978-01-01

    Using large-scale N-body calculations for flat disk galaxies, we examine the effect of reversing the angular momentum for various fractions of the stars upon the global bar-forming mode. The initial conditions for these simulations are based on stationary states of two classes of models: the isochrones studied recently by Kalnajs by means of linear theory, and a model resembling the Schmidt model of our own Galaxy. In both cases, as the fraction of retrograde stars is increased, the growth of the bar-forming mode is inhibited (although not eliminated). These N-body results for the isochrones agree with the predictions of linear theory, quantitatively as well as qualitatively.

  4. VizieR Online Data Catalog: Mass models for 175 disk galaxies with SPARC (Lelli+, 2016)

    Science.gov (United States)

    Lelli, F.; McGaugh, S. S.; Schombert, J. M.

    2017-02-01

    Created by team leaders Federico Lelli and Stacy McGaugh (CWRU Astronomy) and Jim Schombert (UOregon Physics), SPARC (Spitzer Photometry and Accurate Rotation Curves) is a sample of 175 disk galaxies covering a broad range of morphologies (S0 to Irr), luminosities (107 to 1012Lsun), and sizes (0.3 to 15kpc). We collected more than 200 extended HI rotation curves from previous compilations, large surveys, and individual studies. This kinematic data set is the result of ~30yr of interferometric HI observations using the Westerbork Synthesis Radio Telescope (WSRT), Very Large Array (VLA), Australia Telescope Compact Array (ATCA), and Giant Metrewave Radio Telescope (GMRT). Subsequently, we searched the Spitzer archive and found useful [3.6] images for 175 galaxies. Most of these objects are part of the Spitzer Survey for Stellar Structure in Galaxies (S4G; Sheth et al. 2010, Cat. J/PASP/122/1397). We also used [3.6] images from Schombert & McGaugh 2014PASA...31...11S for low-surface-brightness (LSB) galaxies (3 data files).

  5. No more active galactic nuclei in clumpy disks than in smooth galaxies at z ∼ 2 in CANDELS/3D-HST

    Energy Technology Data Exchange (ETDEWEB)

    Trump, Jonathan R.; Luo, Bin; Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Barro, Guillermo; Guo, Yicheng; Koo, David C.; Faber, S. M. [University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Juneau, Stéphanie [Irfu/Service d' Astrophysique, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France); Weiner, Benjamin J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Brammer, Gabriel B.; Ferguson, Henry C.; Grogin, Norman A.; Kartaltepe, Jeyhan; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Dekel, Avishai [Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Hopkins, Philip F. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); McIntosh, Daniel H. [Department of Physics and Astronomy, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Momcheva, Ivelina [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others

    2014-10-01

    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ∼ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ∼ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ∼ 1.85—whether violent disk instabilities or secular processes—are as efficient in smooth galaxies as they are in clumpy galaxies.

  6. On the origin of bursts in blue compact dwarf galaxies: clues from kinematics and stellar populations

    CERN Document Server

    Koleva, M; Zeilinger, W W; Verbeke, R; Schroyen, J; Vermeylen, L

    2014-01-01

    Blue compact dwarf galaxies (BCDs) form stars at, for their sizes, extraordinarily high rates. In this paper, we study what triggers this starburst and what is the fate of the galaxy once its gas fuel is exhausted. We select four BCDs with smooth outer regions, indicating them as possible progenitors of dwarf elliptical galaxies. We have obtained photometric and spectroscopic data with the FORS and ISAAC instruments on the VLT. We analyse their infra-red spectra using a full spectrum fitting technique which yields the kinematics of their stars and ionized gas together with their stellar population characteristics. We find that the_stellar_ velocity to velocity dispersion ratio (v/sigma) of our BCDs is of the order of 1.5, similar to that of dwarf elliptical galaxies. Thus, those objects do not require significant (if any) loss of angular momentum to fade into early type dwarfs. This finding is in discordance with previous studies, which however compared the stellar kinematics of dwarf elliptical galaxies with...

  7. The Extraordinary Mid-infrared Spectrum of the Blue Compact Dwarf Galaxy SBS0335-052

    CERN Document Server

    Houck, J R; Brandl, B R; Weedman, D; Herter, T; Uchida, K I; Armus, L; Soifer, B T; Bernard-Salas, J; Spoon, H W W; Devost, D

    2004-01-01

    SBS0335-052 is a blue compact dwarf galaxy (BCD) with one of the lowest known metallicities, Z$\\sim$Z$_{\\sun}$/41, making it a local example of how primordial starburst galaxies and their precursors might appear. A spectrum obtained with the Infrared Spectrograph (IRS) on the Spitzer Space Telescope clearly shows silicate absorption features, emission lines of [SIV] and [NeIII], and puts strong upper limits on the PAH emission features. The observed low resolution spectrum (R~90) extends from 5.3 to 35microns and peaks at ~28microns. The spectrum is compared to IRS observations of the prototypical starburst nucleus NGC7714. SBS0335-052 is quite unlike normal starburst galaxies, which show strong PAH bands, low ionization emission lines, and a continuum peak near 80microns. The continuum difference for $\\lambda >30 \\mu$m implies a substantial reduction in the mass of cold dust. If the spectrum of this very low metallicity galaxy is representative of star forming galaxies at higher redshifts, it may be difficul...

  8. A new model for the gravitational potential perturbations in disks of spiral galaxies. An application to our Galaxy

    CERN Document Server

    Junqueira, T C; Braga, C A S; Barros, D A

    2012-01-01

    We propose a new, more realistic, description of the perturbed gravitational potential of spiral galaxies, with spiral arms having Gaussian-shaped groove profiles. We investigate the stable stellar orbits in galactic disks, using the new perturbed potential. The influence of the bulge mass on the stellar orbits in the inner regions of a disk is also investigated. The new description offers the advantage of easy control of the parameters of the Gaussian profile of its potential. We find a range of values for the perturbation amplitude from 400 to 800 km^2 s^{-2} kpc^{-1} which implies a maximum ratio of the tangential force to the axisymmetric force between 3% and 6%, approximately. Good self-consistency of arm shapes is obtained between the Inner Lindblad resonance (ILR) and the 4:1 resonance. Near the 4:1 resonance the response density starts to deviate from the imposed logarithmic spiral form. This creates bifurcations that appear as short arms. Therefore the deviation from a perfect logarithmic spiral in g...

  9. How does the mass transport in disk galaxy models influence the character of orbits?

    CERN Document Server

    Zotos, Euaggelos E

    2015-01-01

    We explore the regular or chaotic nature of orbits of stars moving in the meridional (R,z) plane of an axially symmetric time-dependent disk galaxy model with a central, spherically symmetric nucleus. In particular, mass is linearly transported from the disk to the galactic nucleus, in order to mimic, in a way, the case of self-consistent interactions of an actual N-body simulation. We thus try to unveil the influence of this mass transportation on the different families of orbits of stars by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families, evolve as the galaxy develops a dense and massive nucleus in its core. The SALI method is applied to samples of orbits in order to distinguish safely between ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics is used for identifying the various families of regular orbits and also for recognizing the secondary resonances that bifurcate from them. Our computat...

  10. Dissecting simulated disk galaxies I: the structure of mono-age populations

    CERN Document Server

    Martig, Marie; Flynn, Chris

    2014-01-01

    We study seven simulated disk galaxies, three with a quiescent merger history, and four with mergers in their last 9 Gyr of evolution. We compare their structure at z=0 by decomposing them into "mono-age populations" (MAPs) of stars within 500 Myr age bins. All studied galaxies undergo a phase of merging activity at high redshift, so that stars older than 9 Gyr are found in a centrally concentrated component, while younger stars are mostly found in disks. We find that most MAPs have simple exponential radial and vertical density profiles, with a scale-height that typically increases with age. Because a large range of merger histories can create populations with simple structures, this suggests that the simplicity of the structure of mono-abundance populations observed in the Milky Way by Bovy et al. (2012b,c) is not necessarily a direct indicator of a quiescent history for the Milky Way. Similarly, the anti-correlation between scale-length and scale-height does not necessarily imply a merger-free history. How...

  11. Simulating realistic disk galaxies with a novel sub-resolution ISM model

    CERN Document Server

    Murante, Giuseppe; Borgani, Stefano; Tornatore, Luca; Dolag, Klaus

    2014-01-01

    We present results of cosmological simulations of disk galaxies carried out with the GADGET-3 TreePM+SPH code, where star formation and stellar feedback are described using our MUlti Phase Particle Integrator (MUPPI) model. This description is based on simple multi-phase model of the interstellar medium at unresolved scales, where mass and energy flows among the components are explicitly followed by solving a system of ordinary differential equations. Thermal energy from SNe is injected into the local hot phase, so as to avoid that it is promptly radiated away. A kinetic feedback prescription generates the massive outflows needed to avoid the over-production of stars. We use two sets of zoomed-in initial conditions of isolated cosmological halos with masses (2-3) * 10^{12} Msun, both available at several resolution levels. In all cases we obtain spiral galaxies with small bulge-over-total stellar mass ratios (B/T \\approx 0.2), extended stellar and gas disks, flat rotation curves and realistic values of stella...

  12. Kiloparsec-scale dust disks in high-redshift luminous submillimeter galaxies

    CERN Document Server

    Hodge, J A; Simpson, J M; Smail, I; Walter, F; Alexander, D M; Bertoldi, F; Biggs, A D; Brandt, W N; Chapman, S C; Chen, C C; Coppin, K E K; Cox, P; Edge, A C; Greve, T R; Ivison, R J; Karim, A; Knudsen, K K; Menten, K M; Rix, H -W; Schinnerer, E; Wardlow, J L; Weiss, A; van der Werf, P

    2016-01-01

    We present high-resolution (0.16$"$) 870um Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous (L_IR ~ 4 x 10^12 L_sun) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z~2.5 galaxies on ~1.3 kpc scales. The emission has a median effective radius of $R_e=0.24" \\pm 0.02"$, corresponding to a typical physical size of $R_{e}=1.8\\pm$0.2 kpc. We derive a median S\\'ersic index of $n=0.9\\pm0.2$, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0.12$"$ (~1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even m...

  13. The ACS Nearby Galaxy Survey Treasury I. The Star Formation History of the M81 Outer Disk

    CERN Document Server

    Williams, Benjamin F; Seth, Anil C; Weisz, Daniel; Dolphin, Andrew; Skillman, Evan; Harris, Jason; Holtzman, Jon; Girardi, Leo; de Jong, Roelof S; Olsen, Knut; Cole, Andrew; Gallart, Carme; Gogarten, Stephanie M; Hidalgo, Sebastian L; Mateo, Mario; Rosema, Keith; Stetson, Peter B; Quinn, Thomas

    2008-01-01

    The ACS Nearby Galaxy Survey Treasury (ANGST) is a large Hubble Space Telescope (HST) Advanced Camera for Surveys (ACS) treasury program to obtain resolved stellar photometry for a volume-limited sample of galaxies out to 4 Mpc. As part of this program, we have obtained deep ACS imaging of a field in the outer disk of the large spiral galaxy M81. The field contains the outskirts of a spiral arm as well as an area containing no current star formation. Our imaging results in a color-magnitude diagram (CMD) reaching to F814W = 28.8 and F606W = 29.5, one magnitude fainter than the red clump. Through detailed modeling of the full CMD, we quantify the age and metallicity distribution of the stellar populations contained in the field. The mean metallicity in the field is -1~100 Myr. We discuss the measured evolution of the M81 disk in the context of surveys of high-redshift disk galaxies and deep stellar photometry of other nearby galaxies. All of these indicate that massive spiral disks are mostly formed by z~1 and...

  14. VLT/GIRAFFE spectroscopic observations of the metal-poor blue compact dwarf galaxy SBS 0335-052E

    Science.gov (United States)

    Izotov, Y. I.; Schaerer, D.; Blecha, A.; Royer, F.; Guseva, N. G.; North, P.

    2006-11-01

    Aims.We present two-dimensional spectroscopy of the extremely metal-deficient blue compact dwarf (BCD) galaxy SBS 0335-052E to study physical conditions, element abundances and kinematical properties of the ionised gas in this galaxy. Methods: .Observations were obtained in the spectral range λ3620-9400 Å with the imaging spectrograph GIRAFFE on the UT2 of the Very Large Telescope (VLT). These observations are the first ones carried out so far with GIRAFFE in the ARGUS mode which allows one to simultaneously obtain 308 spectra covering a 11.4 arcsec×7.3 arcsec region. Results: .We produced images of SBS 0335-052E in the continuum and in emission lines of different stages of excitation. While the maximum of emission in the majority of lines, including the strong lines Hβ 4861 Å, Hα 6563 Å, [O iii] 4363,5007 Å, [O ii] 3726,3729 Å, coincides with the youngest south-eastern star clusters 1 and 2, the emission of He II 4686 Å line is offset to the more evolved north-west clusters 4, 5. This suggests that hard ionising radiation responsible for the He II λ4686 Å emission is not related to the most massive youngest stars, but rather is related to fast radiative shocks. This conclusion is supported by the kinematical properties of the ionised gas from the different emission lines as the velocity dispersion in the He II λ4686 Å line is systematically higher, by ~50-100%, than that in other lines. The variations of the emission line profiles suggest the presence of an ionised gas outflow in the direction perpendicular to the galaxy disk. We find a relatively high electron number density Ne of several hundred cm-3 in the brightest part of SBS 0335-052E. There is a small gradient of the electron temperature Te and oxygen abundance from the East to the West with systematically higher Te and lower 12+log O/H in the western part of the galaxy. The oxygen abundances for the whole H II region and its brightest part are 12 + log O/H = 7.29 ± 0.02 and 7.31 ± 0

  15. Modelling the spectral energy distribution of galaxies. V. The dust and PAH emission SEDs of disk galaxies

    CERN Document Server

    Popescu, Cristina C; Dopita, Michael A; Fischera, Joerg; Kylafis, Nikolaos D; Madore, Barry F

    2010-01-01

    We present a self-consistent model of the spectral energy distributions (SEDs) of spiral galaxies from the ultraviolet (UV) to the mid-infrared (MIR)/far-infrared (FIR)/submillimeter (submm) based on a full radiative transfer calculation of the propagation of starlight in galaxy disks. This model predicts not only the total integrated energy absorbed in the UV/optical and re-emitted in the infrared/submm, but also the colours of the dust emission based on an explicit calculation of the strength and colour of the UV/optical radiation fields heating the dust, and incorporating a full calculation of the stochastic heating of small dust grains and PAH molecules. The geometry of the translucent components of the model is empirically constrained using the results from the radiation transfer analysis of Xilouris et al. on spirals in the middle range of the Hubble sequence, while the geometry of the optically thick components is constrained from physical considerations with a posteriori checks of the model prediction...

  16. Multiwavelength Observations of the Low Metallicity Blue Compact Dwarf Galaxy SBS 0335-052

    CERN Document Server

    Dale, D A; Neugebauer, G; Soifer, B T; Frayer, D T; Condon, J J; Dale, Daniel A.; Helou, George; Neugebauer, Gerry; Frayer, David T.; Condon, James J.

    2001-01-01

    New infrared and millimeter observations from Keck, Palomar, ISO, and OVRO and archival data from the NRAO VLA and IRAS are presented for the low metallicity blue compact dwarf galaxy SBS 0335-052. Mid-infrared imaging shows this young star-forming system is compact (0.31"; 80 pc) at 12.5 microns. The large Br-gamma equivalent width (235 Angstroms) measured from integral field spectroscopy is indicative of a ~5 Myr starburst. The central source appears to be optically thin in emission, containing both a warm (~80 K) and a hot (~210 K) dust component, and the overall interstellar radiation field is quite intense, about 10,000 times the intensity in the solar neighborhood. CO emission is not detected, though the galaxy shows an extremely high global H I gas-to-dust mass ratio, high even for blue compact dwarfs. Finally, the galaxy's mid-infrared-to-optical and mid-to-near-infrared luminosity ratios are quite high, whereas its far-infrared-to-radio and far-infrared-to-optical flux ratios are surprisingly similar...

  17. Kiloparsec-scale Dust Disks in High-redshift Luminous Submillimeter Galaxies

    Science.gov (United States)

    Hodge, J. A.; Swinbank, A. M.; Simpson, J. M.; Smail, I.; Walter, F.; Alexander, D. M.; Bertoldi, F.; Biggs, A. D.; Brandt, W. N.; Chapman, S. C.; Chen, C. C.; Coppin, K. E. K.; Cox, P.; Dannerbauer, H.; Edge, A. C.; Greve, T. R.; Ivison, R. J.; Karim, A.; Knudsen, K. K.; Menten, K. M.; Rix, H.-W.; Schinnerer, E.; Wardlow, J. L.; Weiss, A.; van der Werf, P.

    2016-12-01

    We present high-resolution (0.″16) 870 μm Atacama Large Millimeter/submillimeter Array (ALMA) imaging of 16 luminous ({L}{IR}˜ 4× {10}12 {L}⊙ ) submillimeter galaxies (SMGs) from the ALESS survey of the Extended Chandra Deep Field South. This dust imaging traces the dust-obscured star formation in these z˜ 2.5 galaxies on ˜1.3 kpc scales. The emission has a median effective radius of R e = 0.″24 ± 0.″02, corresponding to a typical physical size of {R}e= 1.8 ± 0.2 kpc. We derive a median Sérsic index of n = 0.9 ± 0.2, implying that the dust emission is remarkably disk-like at the current resolution and sensitivity. We use different weighting schemes with the visibilities to search for clumps on 0.″12 (˜1.0 kpc) scales, but we find no significant evidence for clumping in the majority of cases. Indeed, we demonstrate using simulations that the observed morphologies are generally consistent with smooth exponential disks, suggesting that caution should be exercised when identifying candidate clumps in even moderate signal-to-noise ratio interferometric data. We compare our maps to comparable-resolution Hubble Space Telescope {H}160-band images, finding that the stellar morphologies appear significantly more extended and disturbed, and suggesting that major mergers may be responsible for driving the formation of the compact dust disks we observe. The stark contrast between the obscured and unobscured morphologies may also have implications for SED fitting routines that assume the dust is co-located with the optical/near-IR continuum emission. Finally, we discuss the potential of the current bursts of star formation to transform the observed galaxy sizes and light profiles, showing that the z˜ 0 descendants of these SMGs are expected to have stellar masses, effective radii, and gas surface densities consistent with the most compact massive ({M}* ˜ 1-2 × 1011 {M}⊙ ) early-type galaxies observed locally.

  18. Blue Supergiant X-Ray Binaries in the Nearby Dwarf Galaxy IC 10

    Science.gov (United States)

    Laycock, Silas G. T.; Christodoulou, Dimitris M.; Williams, Benjamin F.; Binder, Breanna; Prestwich, Andrea

    2017-02-01

    In young starburst galaxies, the X-ray population is expected to be dominated by the relics of the most massive and short-lived stars, black hole and neutron-star high-mass X-ray binaries (XRBs). In the closest such galaxy, IC 10, we have made a multi-wavelength census of these objects. Employing a novel statistical correlation technique, we have matched our list of 110 X-ray point sources, derived from a decade of Chandra observations, against published photometric data. We report an 8σ correlation between the celestial coordinates of the two catalogs, with 42 X-ray sources having an optical counterpart. Applying an optical color–magnitude selection to isolate blue supergiant (SG) stars in IC 10, we find 16 matches. Both cases show a statistically significant overabundance versus the expectation value for chance alignments. The blue objects also exhibit systematically higher {f}x/{f}v ratios than other stars in the same magnitude range. Blue SG-XRBs include a major class of progenitors of double-degenerate binaries, hence their numbers are an important factor in modeling the rate of gravitational-wave sources. We suggest that the anomalous features of the IC 10 stellar population are explained if the age of the IC 10 starburst is close to the time of the peak of interaction for massive binaries.

  19. Extragalactic archeology with the GHOSTS Survey I. - Age-resolved disk structure of nearby low-mass galaxies

    CERN Document Server

    Streich, David; Bailin, Jeremy; Bell, Eric F; Holwerda, Benne W; Minchev, Ivan; Monachesi, Antonela; Radburn-Smith, David J

    2016-01-01

    We study the individual evolution histories of three nearby low-mass edge-on galaxies (IC 5052, NGC4244, and NGC5023). Using resolved stellar populations, we constructed star count density maps for populations of different ages and analyzed the change of structural parameters with stellar age within each galaxy. We do not detect a separate thick disk in any of the three galaxies, even though our observations cover a wider range in equivalent surface brightness than any integrated light study. While scale heights increase with age, each population can be well described by a single disk. Two of the galaxies contain a very weak additional component, which we identify as the faint halo. The mass of these faint halos is lower than 1% of the mass of the disk. The three galaxies show low vertical heating rates, which are much lower than the heating rate of the Milky Way. This indicates that heating agents, such as giant molecular clouds and spiral structure, are weak in low-mass galaxies. All populations in the thre...

  20. Formation and Evolution of the Dust in Galaxies. III. The Disk of the Milky Way

    CERN Document Server

    Piovan, L; Merlin, E; Grassi, T; Tantalo, R; Buonomo, U; Cassarà, L P

    2011-01-01

    Models of chemical evolution of galaxies including the dust are nowadays required to decipher the high-z universe. In a series of three papers we have tackled the problem and set a modern chemical evolution model. In the first paper (Piovan et al., 2011a) we revised the condensation coefficients for the elements that typically are present in the dust. In the second paper (Piovan et al., 2011b) we have implemented the dust into the Padova chemical model and tested it against the observational data for the Solar Neighbourhood. In this paper we extend it to the whole Disk of the Milky Way (MW). The Disk is used as a laboratory to analyze the spatial and temporal behaviour of (i) several dust grain families with the aid of which we can describe the ISM, (ii) the abundances in the gas, dust, and total ISM of the elements present in the dust and (iii) the depletion of the same elements. The temporal evolution of the dust and gas across the Disk is calculated under the effect of radial flows and a central Bar. The g...

  1. Indications of M-dwarf Deficits in the Halo and Thick Disk of the Galaxy

    CERN Document Server

    Konishi, Mihoko; Sumi, Takahiro; Fukagawa, Misato; Matsuo, Taro; Samland, Matthias S; Yamamoto, Kodai; Sudo, Jun; Itoh, Yoichi; Arimoto, Nobuo; Kajisawa, Masaru; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D; Carson, Joseph; Currie, Thayne; Egner, Sebastian E; Feldt, Markus; Goto, Miwa; Grady, Carol A; Guyon, Olivier; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S; Henning, Thomas; Hodapp, Klaus W; Ishii, Miki; Iye, Masanori; Janson, Markus; Kandori, Ryo; Knapp, Gillian R; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Kuzuhara, Masayuki; Kwon, Jungmi; McElwain, Michael W; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martín, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takahashi, Yasuhiro H; Takami, Hideki; Takato, Naruhisa; Terada, Hiroshi; Thalmann, Christian; Tomono, Daigo; Turner, Edwin L; Usuda, Tomonori; Watanabe, Makoto; Wisniewski, John P; Yamada, Toru; Tamura, Motohide

    2014-01-01

    We compared the number of faint stars detected in deep survey fields with the current stellar distribution model of the Galaxy and found that the detected number in the H band is significantly smaller than the predicted number. This indicates that M-dwarfs, the major component, are fewer in the halo and the thick disk. We used archived data of several surveys in both the north and south field of GOODS (Great Observatories Origins Deep Survey), MODS in GOODS-N, and ERS and CANDELS in GOODS-S. The number density of M-dwarfs in the halo has to be 20+/-13% relative to that in the solar vicinity, in order for the detected number of stars fainter than 20.5 mag in the H band to match with the predicted value from the model. In the thick disk, the number density of M-dwarfs must be reduced (52+/-13%) or the scale height must be decreased (~600 pc). Alternatively, overall fractions of the halo and thick disks can be significantly reduced to achieve the same effect, because our sample mainly consists of faint M-dwarfs....

  2. Indications of M-Dwarf Deficits in the Halo and Thick Disk of the Galaxy

    Science.gov (United States)

    Konishi, Mihoko; Shibai, Hiroshi; Sumi, Takahiro; Fukagawa, Misato; Matsuo, Taro; Samland, Matthias S.; Yamamoto, Kodai; Sudo, Jun; Itoh, Yoichi; Arimoto, Nobuo; Kajisawa, Masaru; Abe, Lyu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Feldt, Marcus; Goto, Miwa; Grady, Carol A.; Guyon, Oliver; Hashimoto, Jun; Hayano, Yutaka; Hayashi, Masahiko; McElwain, Michael W.

    2014-01-01

    We compared the number of faint stars detected in deep survey fields with the current stellar distribution model of the Galaxy and found that the detected number in the H band is significantly smaller than the predicted number. This indicates that M-dwarfs, the major component, are fewer in the halo and the thick disk. We used archived data of several surveys in both the north and south field of GOODS (Great Observatories Origins Deep Survey), MODS in GOODS-N, and ERS and CANDELS in GOODS-S. The number density of M-dwarfs in the halo has to be 20+/-13% relative to that in the solar vicinity, in order for the detected number of stars fainter than 20.5 mag in the H band to match with the predicted value from the model. In the thick disk, the number density of M-dwarfs must be reduced (52+/-13%) or the scale height must be decreased ( approx. 600 pc). Alternatively, overall fractions of the halo and thick disks can be significantly reduced to achieve the same effect, because our sample mainly consists of faint M-dwarfs. Our results imply that the M-dwarf population in regions distant from the Galactic plane is significantly smaller than previously thought. We then discussed the implications this has on the suitability of the model predictions for the prediction of non-companion faint stars in direct imaging extrasolar planet surveys by using the best-fit number densities.

  3. Formation and Hardening of Supermassive Black Hole Binaries in Minor Mergers of Disk Galaxies

    CERN Document Server

    Khan, Fazeel Mahmood; Berczik, Peter; Just, Andreas; Mayer, Lucio; Nitadori, Keigo; Callegari, Simone

    2012-01-01

    We model for the first time the complete orbital evolution of a pair of Supermassive Black Holes (SMBHs) in a 1:10 galaxy merger of two disk dominated gas-rich galaxies, from the stage prior to the formation of the binary up to the onset of gravitational wave emission when the binary separation has shrunk to 1 milli parsec. The high-resolution smoothed particle hydrodynamics (SPH) simulations used for the first phase of the evolution include star formation, accretion onto the SMBHs as well as feedback from supernovae explosions and radiative heating from the SMBHs themselves. Using the direct N-body code \\phi-GPU we evolve the system further without including the effect of gas, which has been mostly consumed by star formation in the meantime. We start at the time when the separation between two SMBHs is ~ 700 pc and the two black holes are still embedded in their galaxy cusps. We use 3 million particles to study the formation and evolution of the SMBH binary till it becomes hard. After a hard binary is formed...

  4. A Test of Star Formation Laws in Disk Galaxies. II. Dependence on dynamical properties

    CERN Document Server

    Suwannajak, Chutipong; Leroy, Adam K

    2014-01-01

    We use observed radial profiles of mass surface densities of total, $\\Sigma_g$, & molecular, $\\Sigma_{\\rm H2}$, gas, rotation velocity & star formation rate (SFR) surface density, $\\Sigma_{\\rm sfr}$, of the molecular-rich ($\\Sigma_{\\rm H2}\\ge\\Sigma_{\\rm HI}/2$) regions of 16 nearby disk galaxies to test several star formation laws: a Kennicutt-Schmidt law, $\\Sigma_{\\rm sfr}=A_g\\Sigma_{g,2}^{1.5}$; a Constant Molecular law, $\\Sigma_{\\rm sfr}=A_{\\rm H2}\\Sigma_{\\rm H2,2}$; the turbulence-regulated laws of Krumholz & McKee (KM05) and Krumholz et al. (KMT09), a Gas-$\\Omega$ law, $\\Sigma_{\\rm sfr}=B_\\Omega\\Sigma_g\\Omega$; and a shear-driven GMC Collision law, $\\Sigma_{\\rm sfr}=B_{\\rm CC}\\Sigma_g\\Omega(1-0.7\\beta)$, where $\\beta\\equiv d {\\rm ln} v_{\\rm circ}/d {\\rm ln} r$. If allowed one free normalization parameter for each galaxy, these laws predict the SFR with rms errors of factors of 1.4 - 1.8. If a single normalization parameter is used by each law for the entire galaxy sample, then rms errors rang...

  5. Metallicity and Age of the Stellar Stream Around the Disk Galaxy NGC 5907

    CERN Document Server

    Laine, Seppo; Capak, Peter; Arendt, Richard G; Romanowsky, Aaron J; Martinez-Delgado, David; Ashby, Matthew L N; Davies, James E; Majewski, Stephen R; Brodie, Jean P; GaBany, R Jay; Arnold, Jacob A

    2016-01-01

    Stellar streams have become central to studies of the interaction histories of nearby galaxies. To characterize the most prominent parts of the stellar stream around the well-known nearby (d = 17 Mpc) edge-on disk galaxy NGC 5907, we have obtained and analyzed new, deep gri Subaru/Suprime-Cam and 3.6 micron Spitzer/Infrared Array Camera (IRAC) observations. Combining the near-infrared 3.6 micron data with visible-light images allows us to use a long wavelength baseline to estimate the metallicity and age of the stellar population along a ~60 kpc long segment of the stream. We have fitted the stellar spectral energy distribution (SED) with a single-burst stellar population synthesis model and we use it to distinguish between the proposed satellite accretion and minor/major merger formation models of the stellar stream around this galaxy. We conclude that a massive minor merger (stellar mass ratio of at least 1:8) can best account for the metallicity of -0.3 inferred along the brightest parts of the stream.

  6. Bulge-forming galaxies with an extended rotating disk at z~2

    CERN Document Server

    Tadaki, Ken-ichi; Kodama, Tadayuki; Wuyts, Stijn; Wisnioski, Emily; Schreiber, Natascha M Förster; Burkert, Andreas; Lang, Philipp; Tacconi, Linda J; Lutz, Dieter; Belli, Sirio; Davies, Richard I; Hatsukade, Bunyo; Hayashi, Masao; Herrera-Camus, Rodrigo; Ikarashi, Soh; Inoue, Shigeki; Kohno, Kotaro; Koyama, Yusei; Mendel, J Trevor; Nakanishi, Kouichiro; Shimakawa, Rhythm; Suzuki, Tomoko L; Tamura, Yoichi; Tanaka, Ichi; Übler, Hannah; Wilman, Dave J

    2016-01-01

    We present 0".2-resolution Atacama Large Millimeter/submillimeter Array observations at 870 um for 25 Halpha-seleced star-forming galaxies (SFGs) around the main-sequence at z=2.2-2.5. We detect significant 870 um continuum emission in 16 (64%) of these SFGs. The high-resolution maps reveal that the dust emission is mostly radiated from a single region close to the galaxy center. Exploiting the visibility data taken over a wide $uv$ distance range, we measure the half-light radii of the rest-frame far-infrared emission for the best sample of 12 SFGs. We find nine galaxies to be associated with extremely compact dust emission with R_{1/2,870um}1e10 Msol/kpc^2 in several hundred Myr, i.e. by z~2. Moreover, ionized gas kinematics reveal that they are rotation-supported with an angular momentum as large as that of typical SFGs at z=1-3. Our results suggest bulges are commonly formed in extended rotating disks by internal processes, not involving major mergers.

  7. On the effective oxygen yield in the disks of spiral galaxies

    CERN Document Server

    Zasov, A; Abramova, O

    2015-01-01

    The factors influencing chemical evolution of galaxies are poorly understood. Both gas inflow and gas outflow reduce a gas-phase abundance of heavy elements (metallicity) whereas the ongoing star formation continuously increases it. To exclude the stellar nucleosynthesis from consideration, we analyze for the sample of 14 spiral galaxies the radial distribution of the effective yield of oxygen $y_{eff}$, which would be identical to the true stellar yield (per stellar generation) $y_o$ if the evolution followed the closed box model. As the initial data for gas-phase abundance we used the O/H radial profiles from Moustakas, Kennicutt, Tremonti et al. (2010), based on two different calibrations (Pilyugin & Thuan 2005 (PT2005) and Kobulnicky & Kewley 2004 (KK2004) methods). In most of galaxies with the PT2005 calibration, which we consider as a preferred one, the yield $y_{eff}$ in the main disk ($R \\ge 0.2~R_{25}$, where $R_{25}$ is the optical radius) increases with radius, remaining lower than the empi...

  8. Halo Gas and Galaxy Disk Kinematics of a Volume-Limited Sample of MgII Absorption-Selected Galaxies at z~0.1

    CERN Document Server

    Kacprzak, G G; Barton, E J; Cooke, J

    2011-01-01

    We have directly compared MgII halo gas kinematics to the rotation velocities derived from emission/absorption lines of the associated host galaxies. Our 0.096galaxies, with impact parameters of 12-90 kpc from background quasars sight-lines, associated with 11 MgII absorption systems with MgII equivalent widths 0.3< W_r(2796)<2.3A. For only 5/13 galaxies, the absorption resides to one side of the galaxy systemic velocity and trends to align with one side of the galaxy rotation curve. The remainder have absorption that spans both sides of the galaxy systemic velocity. These results differ from those at z~0.5, where 74% of the galaxies have absorption residing to one side of the galaxy systemic velocity. For all the z~0.1 systems, simple extended disk-like rotation models fail to reproduce the full MgII velocity spread, implying other dynamical processes contribute to the MgII kinematics. In fact 55% of the galaxies are "counter-rotating" with respect ...

  9. Compaction and Quenching of High-z Galaxies: Blue and Red Nuggets in Cosmological Simulations

    CERN Document Server

    Zolotov, Adi; Mandelker, Nir; Tweed, Dylan; Inoue, Shigeki; DeGraf, Colin; Ceverino, Daniel; Primack, Joel

    2014-01-01

    We use cosmological simulations to study a characteristic evolution pattern of high redshift galaxies. Early, stream-fed, highly perturbed, gas-rich discs undergo phases of dissipative contraction into compact, star-forming systems (blue nuggets) at z~4-2. The peak of gas compaction marks the onset of central gas depletion and inside-out quenching into compact ellipticals (red nuggets) by z~2. These are sometimes surrounded by gas rings or grow extended dry stellar envelopes. The compaction occurs at a roughly constant specific star-formation rate (SFR), and the quenching occurs at a constant stellar surface density within the inner kpc (Sigma_1). Massive galaxies quench earlier, faster, and at a higher Sigma_1 than lower-mass galaxies, which compactify and attempt to quench more than once. This evolution pattern is consistent with the way galaxies populate the SFR-radius-mass space, and with gradients and scatter across the main sequence. The compaction is triggered by an intense inflow episode, involving me...

  10. The HI content of extremely metal-deficient blue compact dwarf galaxies

    CERN Document Server

    Thuan, T X; Hibbard, J E; Izotov, Y I; Hunt, L K

    2016-01-01

    We have obtained new HI observations with the 100m Green Bank Telescope (GBT) for a sample of 29 extremely metal-deficient star-forming Blue Compact Dwarf (BCD) galaxies, selected from the Sloan Digital Sky Survey spectral data base to be extremely metal-deficient (12+logO/H<7.6). Neutral hydrogen was detected in 28 galaxies, a 97% detection rate. Combining the HI data with SDSS optical spectra for the BCD sample and adding complementary galaxy samples from the literature to extend the metallicity and mass ranges, we have studied how the HI content of a galaxy varies with various global galaxian properties. There is a clear trend of increasing gas mass fraction with decreasing metallicity, mass and luminosity. We obtain the relation M(HI)/L(g)~L(g)^{-0.3}, in agreement with previous studies based on samples with a smaller luminosity range. The median gas mass fraction f(gas) for the GBT sample is equal to 0.94 while the mean gas mass fraction is 0.90+/-0.15, with a lower limit of ~0.65. The HI depletion ti...

  11. THE METALLICITY EVOLUTION OF BLUE COMPACT DWARF GALAXIES FROM THE INTERMEDIATE REDSHIFT TO THE LOCAL UNIVERSE

    Energy Technology Data Exchange (ETDEWEB)

    Lian, Jianhui; Hu, Ning; Ye, Chengyun; Kong, Xu [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Fang, Guanwen, E-mail: ljhhw@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003 (China)

    2016-03-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range of [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope. More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evolution of the metallicity, star formation rate (SFR), and D{sub n}(4000) index. Compared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but a similar O32 ratio. Interestingly, no significant deviation in the mass–metallicity (MZ) relation was found between the intermediate-z and local BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak dependence on redshift. The intermediate-z BCDs seemed to be younger than the local BCDs with lower D{sub n}(4000) index values. The insignificant deviation in the mass–metallicity and mass–SFR relations between intermediate-z and local BCDs indicates that the relations between the global parameters of low-mass compact galaxies may be universal. These results from low-mass compact galaxies could be used to place important observational constraints on galaxy formation and evolution models.

  12. The tidally disturbed luminous compact blue galaxy Mkn 1087 and its surroundings

    CERN Document Server

    Lopez-Sanchez, A R; Rodríguez, M; Lopez-Sanchez, Angel R.; Esteban, Cesar; Rodriguez, Monica

    2004-01-01

    We present new broad-band optical and near-infrared CCD imaging together with deep optical intermediate-resolution spectroscopy of Mkn 1087 and its surrounding objects. We analyze the morphology and colors of the stellar populations of the brightest objects, some of them star-formation areas, as well as the kinematics, physical conditions and chemical composition of the ionized gas associated with them. Mkn 1087 does not host an Active Galactic Nucleus, but it could be a Luminous Compact Blue Galaxy. Although it was classified as a suspected Wolf-Rayet galaxy, we do not detect the spectral features of these sort of massive stars. Mkn 1087 shows morphological and kinematical features that can be explained assuming that it is in interaction with two nearby galaxies: the bright KPG 103a and a dwarf ($M_B\\sim-18$) star-forming companion. We argue that this dwarf companion is not a tidal object but an external galaxy because of its low metallicity [12+log(O/H) = 8.24] with respect to the one derived for Mkn 1087 [...

  13. Triple Scoop from Galaxy Hunter

    Science.gov (United States)

    2006-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Figure 1Figure 2Figure 3 Silver Dollar Galaxy: NGC 253 (figure 1) Located 10 million light-years away in the southern constellation Sculptor, the Silver Dollar galaxy, or NGC 253, is one of the brightest spiral galaxies in the night sky. In this edge-on view from NASA's Galaxy Evolution Explorer, the wisps of blue represent relatively dustless areas of the galaxy that are actively forming stars. Areas of the galaxy with a soft golden glow indicate regions where the far-ultraviolet is heavily obscured by dust particles. Gravitational Dance: NGC 1512 and NGC 1510 (figure 2) In this image, the wide ultraviolet eyes of NASA's Galaxy Evolution Explorer show spiral galaxy NGC 1512 sitting slightly northwest of elliptical galaxy NGC 1510. The two galaxies are currently separated by a mere 68,000 light-years, leading many astronomers to suspect that a close encounter is currently in progress. The overlapping of two tightly wound spiral arm segments makes up the light blue inner ring of NGC 1512. Meanwhile, the galaxy's outer spiral arm is being distorted by strong gravitational interactions with NGC 1510. Galaxy Trio: NGC 5566, NGC 5560, and NGC 5569 (figure 3) NASA's Galaxy Evolution Explorer shows a triplet of galaxies in the Virgo cluster: NGC 5560 (top galaxy), NGC 5566 (middle galaxy), and NGC 5569 (bottom galaxy). The inner ring in NGC 5566 is formed by two nearly overlapping bright arms, which themselves spring from the ends of a central bar. The bar is not visible in ultraviolet because it consists of older stars or low mass stars that do not emit energy at ultraviolet wavelengths. The outer disk of NGC 5566 appears warped, and the disk of NGC 5560 is clearly disturbed. Unlike its galactic neighbors, the disk of NGC 5569 does not appear to have been distorted by any passing galaxies.

  14. VizieR Online Data Catalog: Disk galaxies at 0.1

    Science.gov (United States)

    Boehm, A.; Ziegler, B. L.

    2016-06-01

    Redshifts, maximum rotation velocities, (Johnson) B-band absolute magnitudes and sizes are presented for a sample of 124 disk galaxies covering redshifts 0.1flat cosmology with H0=70km/s/Mpc, Omegamatter=0.3 and Omegalambda=0.7. (1 data file).

  15. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present ionized-gas ([Oiii]λ5007 Å) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (hR). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 Å observed at a mea

  16. The DiskMass Survey : VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    NARCIS (Netherlands)

    Martinsson, Thomas P. K.; Verheijen, Marc A. W.; Westfall, Kyle B.; Bershady, Matthew A.; Schechtman-Rook, Andrew; Andersen, David R.; Swaters, Rob A.

    2013-01-01

    We present ionized-gas ([OIII]lambda 5007 angstrom) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as many as three K-band disk scale lengths (h(R)). These data have been derived from PPak integral-field-unit spectroscopy from 4980-5370 angs

  17. Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-forming Galaxies

    NARCIS (Netherlands)

    Usero, Antonio; Leroy, Adam K.; Walter, Fabian; Schruba, Andreas; García-Burillo, Santiago; Sandstrom, Karin; Bigiel, Frank; Brinks, Elias; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl-Friedrich; de Blok, W. J. G.

    2015-01-01

    We present a new survey of HCN(1-0) emission, a tracer of dense molecular gas, focused on the little-explored regime of normal star-forming galaxy disks. Combining HCN, CO, and infrared (IR) emission, we investigate the role of dense gas in star formation, finding systematic variations in both the a

  18. Catalog of Galaxy Morphology in Four Rich Clusters: Luminosity Evolution of Disk Galaxies at 0.33

    CERN Document Server

    Saintonge, A; Ellingson, E; Yee, H K C; Carlberg, R G; Saintonge, Amelie; Schade, David; Ellingson, Erica; Yee, Howard K.C.; Carlberg, Raymond G.

    2005-01-01

    Hubble Space Telescope (HST) imaging of four rich, X-ray luminous, galaxy clusters (0.33galaxies in their fields. Catalogs of these measurements are presented for 1642 galaxies brighter than F814W(AB)=23.0 . Galaxy luminosity profiles are fitted with three models: exponential disk, de Vaucouleurs bulge, and a disk-plus-bulge hybrid model. The best fit is selected and produces a quantitative assessment of the morphology of each galaxy: the principal parameters derived being B/T, the ratio of bulge to total luminosity, the scale lengths and half-light radii, axial ratios, position angles and surface brightnesses of each component. Cluster membership is determined using a statistical correction for field galaxy contamination, and a mass normalization factor (mass within boundaries of the observed fields) is derived for each cluster. In the present paper, this catalog of measurements is used to investigate the luminosity evolution of di...

  19. The Evolution of Massive Morphological Spheroid and Disk Galaxies in CANDELS from 11 to 6 Billion Years Ago

    Science.gov (United States)

    McIntosh, Daniel H.; CANDELS Collaboration

    2017-01-01

    The premiere HST/WFC3 Treasury program CANDELS (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) has produced detailed visual classifications for statistically useful samples of bright (H>24.5mag) galaxies during and after z~2, the epoch of peak galaxy development. By averaging multiple classifications per galaxy that encompass spheroid-only, bulge-dominated, disk-dominated, disk-only, and irregular/peculiar appearances at visible rest-frame wavelengths, we find that 90% of massive (>1e10 Msun) galaxies at 0.62 to mostly Q at later times. Combining morphologies, structural properties, and SF nature, we find clear differences in the histories of spheroid and disk populations that are robust to selections based on visual or Sersic selection, and to either Q/SF divisor. Massive spheroids experience strong number density growth, substantial size growth, and rapid changes in SF fraction suggesting quenching processes that act on theory comparison is needed to better constrain which physical processes drive the transformation and quenching of massive galaxies.

  20. Disk galaxy scaling relations at intermediate redshifts - I. The Tully-Fisher and velocity-size relations

    CERN Document Server

    Boehm, Asmus

    2015-01-01

    Galaxy scaling relations such as the Tully-Fisher relation (between maximum rotation velocity Vmax and luminosity) and the velocity-size relation (between Vmax and disk scale length) are powerful tools to quantify the evolution of disk galaxies with cosmic time. We took spatially resolved slit spectra of 261 field disk galaxies at redshifts up to z~1 using the FORS instruments of the ESO Very Large Telescope. The targets were selected from the FORS Deep Field and William Herschel Deep Field. Our spectroscopy was complemented with HST/ACS imaging in the F814W filter. We analyzed the ionized gas kinematics by extracting rotation curves from the 2-D spectra. Taking into account all geometrical, observational and instrumental effects, these rotation curves were used to derive the intrinsic Vmax. Neglecting galaxies with disturbed kinematics or insufficient spatial rotation curve extent, Vmax could be determined for 137 galaxies covering redshifts 0.05

  1. A Spitzer Study of Pseudobulges in S0 Galaxies: Secular Evolution of Disks

    Science.gov (United States)

    Barway, Sudhanshu; Vaghmare, Kaustubh; Mathur, Smita; Kembhavi, Ajit

    2017-03-01

    A comparison of pseudobulges in S0 and spiral galaxies is presented using structural parameters derived from 2-d decomposition of mid-infrared images taken at 3.6 μm by Spitzer IRAC. The position of the bulges on the Kormendy diagram has been used as an initial classification criterion for determining the nature of the bulge. To make the classification more secure, the criterion proposed by Fisher and Drory (2008) has also been used, which involves using the n = 2 division line on Sérsic index. We find that among the 185 S0 galaxies, 27 are pseudobulge hosts while 160 are classical. Of these 25 pseudobulge hosts, only two belong to the bright luminosity class (MK 22.66, AB system). We find that among spiral galaxies, 77 % (24 of 31) of the bulges are classified as pseudobulges. As pointed out by various studies, the presence of such a large fraction poses problems to our current picture of galaxy formation. How ever, our primary result is that the disk scale length of pseudobulge hosting S0s is significantly smaller on average than that of their spiral counterparts. This can be explained as a lowered disk luminosity which in turn implies that S0s have evolved from spiral progenitors. We also argue that early type spirals are more likely to be the progenitors based on bulge and total luminosity arguments. We speculate that if late type spirals hosting pseudobulges have to evolve into S0s, an additional mechanism along with gas stripping of spirals is needed. We have also investigated the effect of environment on pseudobulges in the two samples, but no significant trends were found in the properties of the pseudobulges as a function of the various structural parameters. The study is made more difficult because of the low number statistics one deals with when the sample is sub-divided based on whether it is in a field or group/cluster environment. The study of pseudobulges based on environment, however, is an interesting one and is something that can be considered

  2. Gemini Observations of Disks and Jets in Young Stellar Objects and in Active Galaxies

    CERN Document Server

    McGregor, Peter; Sutherland, Ralph; Beck, Tracy; Storchi-Bergmann, Thaisa

    2007-01-01

    We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H_2 lines, in accordance with the model advocated by Pyo et al. (2002).

  3. Snap, Crackle, Pop: sub-grid supernova feedback in AMR simulations of disk galaxies

    CERN Document Server

    Rosdahl, Joakim; Dubois, Yohan; Kimm, Taysun; Teyssier, Romain

    2016-01-01

    We compare 5 sub-grid models for supernova (SN) feedback in adaptive mesh refinement (AMR) simulations of isolated dwarf and L-star disk galaxies with 20-40 pc resolution. The models are thermal dump, stochastic thermal, 'mechanical' (injecting energy or momentum depending on the resolution), kinetic, and delayed cooling feedback. We focus on the ability of each model to suppress star formation and generate outflows. Our highest-resolution runs marginally resolve the adiabatic phase of the feedback events, which correspond to 40 SN explosions, and the first three models yield nearly identical results, possibly indicating that kinetic and delayed cooling feedback converge to wrong results. At lower resolution all models differ, with thermal dump feedback becoming inefficient. Thermal dump, stochastic, and mechanical feedback generate multiphase outflows with mass loading factors $\\beta \\ll 1$, which is much lower than observed. For the case of stochastic feedback we compare to published SPH simulations, and fi...

  4. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    CERN Document Server

    Michtchenko, Tatiana A; Barros, Douglas A; Lépine, Jacques R D

    2016-01-01

    Context: Resonances in the stellar orbital motion under perturbations from spiral arms structure play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (for nearly circular orbits), but is not suitable in general. Aims: To expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped profiles, without any restriction on the stellar orbital configurations, and expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes are constructed numerically, in order to characterize the phase-space structure and identify the precise location of the resonances. The study is complemented by the construction of dynamical power spectra, which provide the identif...

  5. The Extended Blue Continuum and Line Emission around the Central Radio Galaxy in Abell 2597

    CERN Document Server

    Koekemoer, A M; Sarazin, C L; McNamara, B R; Donahue, M; Voit, G M; Baum, S A; Gallimore, J F

    1999-01-01

    We present results from detailed imaging of the centrally dominant radio elliptical galaxy in the cooling flow cluster Abell 2597, using data obtained with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). This object is one of the archetypal "blue-lobed" cooling flow radio elliptical galaxies, also displaying a luminous emission-line nebula, a compact radio source, and a significant dust lane and evidence of molecular gas in its center. We show that the radio source is surrounded by a complex network of emission-line filaments, some of which display a close spatial association with the outer boundary of the radio lobes. We present a detailed analysis of the physical properties of ionized and neutral gas associated with the radio lobes, and show that their properties are strongly suggestive of direct interactions between the radio plasma and ambient gas. We resolve the blue continuum emission into a series of knots and clumps, and present evidence that these are most likely du...

  6. SPECTROSCOPY OF LUMINOUS COMPACT BLUE GALAXIES IN DISTANT CLUSTERS. II. PHYSICAL PROPERTIES OF dE PROGENITOR CANDIDATES

    Energy Technology Data Exchange (ETDEWEB)

    Crawford, S. M. [South African Astronomical Observatory, Observatory, 7935 Cape Town (South Africa); Wirth, Gregory D. [W. M. Keck Observatory, 65-1120 Mamalahoa Hwy, Kamuela HI 96743 (United States); Bershady, M. A. [Washburn Observatories, U. Wisconsin—Madison, 475 N. Charter St., Madison, WI 53706 (United States); Randriamampandry, S. M., E-mail: crawford@saao.ac.za, E-mail: gregory.wirth@gmail.com, E-mail: mab@astro.wisc.edu [Astrophysics and Cosmology Research Unit, School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban 4041 (South Africa)

    2016-02-01

    Luminous Compact Blue Galaxies (LCBGs) are an extreme star-bursting population of galaxies that were far more common at earlier epochs than today. Based on spectroscopic and photometric measurements of LCBGs in massive (M > 10{sup 15} M{sub ⊙}), intermediate redshift (0.5 < z < 0.9) galaxy clusters, we present their rest-frame properties including star formation rate, dynamical mass, size, luminosity, and metallicity. The appearance of these small, compact galaxies in clusters at intermediate redshift helps explain the observed redshift evolution in the size–luminosity relationship among cluster galaxies. In addition, we find the rest-frame properties of LCBGs appearing in galaxy clusters are indistinguishable from field LCBGs at the same redshift. Up to 35% of the LCBGs show significant discrepancies between optical and infrared indicators of star formation, suggesting that star formation occurs in obscured regions. Nonetheless, the star formation for LCBGs shows a decrease toward the center of the galaxy clusters. Based on their position and velocity, we estimate that up to 10% of cluster LCBGs are likely to merge with another cluster galaxy. Finally, the observed properties and distributions of the LCBGs in these clusters lead us to conclude that we are witnessing the quenching of the progenitors of dwarf elliptical galaxies that dominate the number density of present-epoch galaxy clusters.

  7. The Rise and Fall of Star Formation Histories of Blue Galaxies at Redshifts 0.2 < z < 1.4

    Science.gov (United States)

    Pacifici, Camilla; Kassin, Susan A.; Weiner, Benjamin; Charlot, Stephane; Gardner, Jonathan P.

    2012-01-01

    Popular cosmological scenarios predict that galaxies form hierarchically from the merger of many progenitor, each with their own unique star formation history (SFH). We use the approach recently developed by Pacifici et al. to constrain the SFHs of 4517 blue (presumably star-forming) galaxies with spectroscopic redshifts in the range O.2 star formation and chemical enrichment histories, stellar population synthesis, nebular emission and attenuation by dust. We constrain the SFH of each galaxy in our sample by comparing the observed fluxes in the B, R,l and K(sub s) bands and rest-frame optical emission-line luminosities with those of one million model spectral energy distributions. We explore the dependence of the resulting SFH on galaxy stellar mass and redshift. We find that the average SFHs of high-mass galaxies rise and fall in a roughly symmetric bell-shaped manner, while those of low-mass galaxies rise progressively in time, consistent with the typically stronger activity of star formation in low-mass compared to high-mass galaxies. For galaxies of all masses, the star formation activity rises more rapidly at high than at low redshift. These findings imply that the standard approximation of exponentially declining SFHs wIdely used to interpret observed galaxy spectral energy distributions is not appropriate to constrain the physical parameters of star-forming galaxies at intermediate redshifts.

  8. The M-sigma relation in simulations of isolated and merging disk galaxies with kinetic or thermal AGN feedback

    CERN Document Server

    Barai, Paramita; Murante, Giuseppe; Gaspari, Massimo; Borgani, Stefano

    2013-01-01

    (Abridged) We investigate two modes of coupling the feedback energy from a central AGN to the neighboring gas in galaxy simulations: kinetic - velocity boost, and thermal - heating. We formulate kinetic feedback models for energy-driven wind (EDW) and momentum-driven wind (MDW), using two free parameters: feedback efficiency epsilon_f, and AGN wind velocity v_w. A novel numerical algorithm is implemented in the SPH code GADGET-3, to prevent the expansion of a hole in the gas distribution around the BH. We perform simulations of isolated evolution and merger of disk galaxies, of Milky-Way mass as well as lower and higher masses. We find that in the isolated galaxy BH kinetic feedback generates intermittent bipolar jet-like gas outflows. We infer that current prescriptions for BH subgrid physics in galaxy simulations can grow the BH to observed values even in an isolated disk galaxy. The BH growth is enhanced in a galaxy merger. Comparing the [M_BH - sigma_star] relation obtained in our simulations with observa...

  9. The gravitational wakefield of a molecular cloud in a disk galaxy

    Science.gov (United States)

    Tagger, M.; Pellat, R.; Sygnet, J. F.

    1990-01-01

    A molecular cloud (considered as a point macroparticle) represents a clump of increased mass density moving in the disk of a galaxy. Its presence generates a gravitational polarization of the disk, somewhat analogous to the polarization of a dielectric medium by a test charged particle. This means that the cloud travels along with a wakefield (a region of increased mass density) which is the collective response of the stars and gas to the perturbing mass. It can represent many times the mass of the cloud, and emits spiral density waves which propagate away. In terms of statistical mechanics, this wakefield will appear as an increased two-particle correlation function which is the equivalent of the Debye sphere in a plasma - despite the absence here of negative charges. At short distances clouds will thus interact through their own gravitational field amplified by their wakefields, which might thus strongly affect their collisionality. Researchers present a calculation of this wakefield and discuss its importance in the collisional dynamics of molecular clouds.

  10. The violent interstellar medium in Milky-Way like disk galaxies

    Science.gov (United States)

    Karoline Walch, Stefanie

    2015-08-01

    Molecular clouds are cold, dense, and turbulent filamentary structures that condense out of the multi-phase interstellar medium. They are also the sites of star formation. The minority of new-born stars is massive, but these stars are particularly important for the fate of their parental molecular clouds as their feedback drives turbulence and regulates star formation.I will present results from the SILCC project (SImulating the Life Cycle of molecular Clouds), in which we study the formation and dispersal of molecular clouds within the multi-phase ISM using high-performance, three-dimensional simulations of representative pieces of disk galaxies. Apart from stellar feedback, self-gravity, an external stellar potential, and magnetic fields, we employ an accurate description of gas heating and cooling as well as a small chemical network including molecule formation and (self-)shielding from the interstellar radiation field. We study the impact of the supernova rate and the positioning of the supernova explosions with respect to the molecular gas in a well defined set of simulations. This allows us to draw conclusions on structure of the multi-phase ISM, the amount of molecular gas formed, and the onset of galactic outflows. Furthermore, we show how important stellar wind feedback is for regulating star formation in these disks.

  11. The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

    Science.gov (United States)

    Kuo, C. Y.; Braatz, J. A.; Condon, J. J.; Impellizzeri, C. M. V.; Lo, K. Y.; Zaw, I.; Schenker, M.; Henkel, C.; Reid, M. J.; Greene, J. E.

    2011-01-01

    Observations of H2O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project (MCP) allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry images and kinematics of water maser emission in six active galaxies: NGC 1194, NGC 2273, NGC 2960 (Mrk 1419), NGC 4388, NGC 6264 and NGC 6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central ~0.3 pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 × 1010 and 61 × 1010 M sun pc-3. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominantly to a supermassive BH. The seven BHs have masses ranging between 0.75 × 107 and 6.5 × 107 M sun, with the mass errors dominated by the uncertainty of the Hubble constant. We compare the megamaser BH mass determination with BH mass measured from the virial estimation method. The virial estimation BH mass in four galaxies is consistent with the megamaser BH mass, but the virial mass uncertainty is much greater. Circumnuclear megamaser disks allow the best mass determination of the central BH mass in external galaxies and significantly improve the observational basis at the low-mass end of the M-σsstarf relation. The M-σsstarf relation may not be a single, low-scatter power law as originally proposed. MCP observations continue and we expect to obtain more maser BH masses in the future.

  12. Classifying orbits of low and high energy stars in axisymmetric disk galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2016-01-01

    The ordered or chaotic character of orbits of stars moving in the meridional $(R,z)$ plane of an analytic axisymmetric time-independent disk galaxy model with an additional spherically symmetric central nucleus is investigated. Our aim is to determine how the total energy influences the orbital structure of the galaxy. For this purpose we monitor how the percentage of chaotic orbits as well as the rates of orbits composing the main regular families evolve as a function of the value of the energy. In order to distinguish with certainty between chaotic and ordered motion we use the SALI method in extensive sets of initial conditions of orbits. Moreover, a spectral method is applied for identifying the various regular families and also for recognizing the secondary resonances that bifurcate from them. Our numerical computations suggest that for low energy levels the observed amount of chaos is high and the orbital content is rather poor, while for high energy levels, corresponding to global motion, regular motio...

  13. SPARC: Mass Models for 175 Disk Galaxies with Spitzer Photometry and Accurate Rotation Curves

    CERN Document Server

    Lelli, Federico; Schombert, James M

    2016-01-01

    We introduce SPARC (Spitzer Photometry & Accurate Rotation Curves): a sample of 175 nearby galaxies with new surface photometry at 3.6 um and high-quality rotation curves from previous HI/Halpha studies. SPARC spans a broad range of morphologies (S0 to Irr), luminosities (~5 dex), and surface brightnesses (~4 dex). We derive [3.6] surface photometry and study structural relations of stellar and gas disks. We find that both the stellar mass-HI mass relation and the stellar radius-HI radius relation have significant intrinsic scatter, while the HI mass-radius relation is extremely tight. We build detailed mass models and quantify the ratio of baryonic-to-observed velocity (Vbar/Vobs) for different characteristic radii and values of the stellar mass-to-light ratio (M/L) at [3.6]. Assuming M/L=0.5 Msun/Lsun (as suggested by stellar population models) we find that (i) the gas fraction linearly correlates with total luminosity, (ii) the transition from star-dominated to gas-dominated galaxies roughly correspond...

  14. NEBULAR AND STELLAR DUST EXTINCTION ACROSS THE DISK OF EMISSION-LINE GALAXIES ON KILOPARSEC SCALES

    Energy Technology Data Exchange (ETDEWEB)

    Hemmati, Shoubaneh; Mobasher, Bahram; Darvish, Behnam [University of California, Riverside, CA 92512 (United States); Nayyeri, Hooshang; Miller, Sarah [University of California, Irvine, CA 92697 (United States); Sobral, David, E-mail: shemm001@ucr.edu [Universidade de Lisboa, PT1349-018 Lisbon (Portugal)

    2015-11-20

    We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z ∼ 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use Hα/Hβ nebular emission line ratios from Keck/DEIMOS high-resolution spectra at each spatial resolution element to measure the amount of attenuation faced by ionized gas at different radii from the centers of galaxies. We find a good agreement between the integrated and median of resolved color excess measurements in our galaxies. The ratio of integrated nebular to stellar dust extinction is always greater than unity, but does not show any trend with stellar mass or star formation rate (SFR). We find that inclination plays an important role in the variation of the nebular to stellar excess ratio. The stellar color excess profiles are found to have higher values at the center compared to outer parts of the disk. However, for lower mass galaxies, a similar trend is not found for the nebular color excess. We find that the nebular color excess increases with stellar mass surface density. This explains the absence of radial trend in the nebular color excess in lower mass galaxies which lack a large radial variation of stellar mass surface density. Using standard conversions of SFR surface density to gas mass surface density, and the relation between dust mass surface density and color excess, we find no significant variation in the dust-to-gas ratio in regions with high gas mass surface densities over the scales probed in this

  15. The WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies

    CERN Document Server

    Riemer--Sørensen, Signe; Parkinson, David; Davis, Tamara M; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Croton, Darren; Drinkwater, Michael J; Forster, Karl; Gilbank, David; Gladders, Mike; Glazebrook, Karl; Jelliffe, Ben; Jurek, Russell J; Li, I-hui; Madore, Barry; Martin, D Christopher; Pimbblet, Kevin; Poole, Gregory B; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted K; Yee, H K C

    2011-01-01

    The absolute neutrino mass scale is currently unknown, but can be constrained from cosmology. The WiggleZ high redshift star-forming blue galaxy sample is less sensitive to systematics from non-linear structure formation, redshift-space distortions and galaxy bias than previous surveys. We obtain a upper limit on the sum of neutrino masses of 0.60eV (95% confidence) for WiggleZ+Wilkinson Microwave Anisotropy Probe. Combining with priors on the Hubble Parameter and the baryon acoustic oscillation scale gives an upper limit of 0.29eV, which is the strongest neutrino mass constraint derived from spectroscopic galaxy redshift surveys.

  16. Halo Gas and Galaxy Disk Kinematics Derived from Observations and LCDM Simulations of MgII Absorption Selected Galaxies at Intermediate Redshift

    CERN Document Server

    Kacprzak, G G; Ceverino, D; Steidel, C C; Klypin, A; Murphy, M T

    2009-01-01

    We obtained ESI/Keck rotation curves of 10 MgII absorption selected galaxies (0.3 < z < 1.0) for which we have WFPC-2/HST images and high resolution HIRES/Keck and UVES/VLT quasar spectra of the MgII absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo MgII absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all cases, a constant rotating thick-disk model poorly reproduces the full spread of observed MgII absorption velocities when reasonably realistic parameters are employed. In 2/10 cases, the galaxy kinematics, star formation surface densities, and absorption kinematics have a resemblance to those of high redshift galaxies showing strong outflows. We find that MgII absorption velocity spread and optical depth distributio...

  17. The H I content of extremely metal-deficient blue compact dwarf galaxies

    Science.gov (United States)

    Thuan, T. X.; Goehring, K. M.; Hibbard, J. E.; Izotov, Y. I.; Hunt, L. K.

    2016-12-01

    We have obtained new H I observations with the 100 m Green Bank Telescope (GBT) for a sample of 29 extremely metal-deficient star-forming blue compact dwarf (BCD) galaxies, selected from the Sloan Digital Sky Survey (SDSS) spectral data base to be extremely metal-deficient (12 + log O/H ≤ 7.6). Neutral hydrogen was detected in 28 galaxies, a 97 per cent detection rate. Combining the H I data with SDSS optical spectra for the BCD sample and adding complementary galaxy samples from the literature to extend the metallicity and mass ranges, we have studied how the H I content of a galaxy varies with various global galaxian properties. There is a clear trend of increasing gas mass fraction with decreasing metallicity, mass and luminosity. We obtain the relation M(H I)/Lg∝ L_g^{-0.3}, in agreement with previous studies based on samples with a smaller luminosity range. The median gas mass fraction fgas for the GBT sample is equal to 0.94 while the mean gas mass fraction is 0.90±0.15, with a lower limit of ˜0.65. The H I depletion time is independent of metallicity, with a large scatter around the median value of 3.4 Gyr. The ratio of the baryonic mass to the dynamical mass of the metal-deficient BCDs varies from 0.05 to 0.80, with a median value of ˜0.2. About 65 per cent of the BCDs in our sample have an effective yield larger than the true yield, implying that the neutral gas envelope in BCDs is more metal-deficient by a factor of 1.5-20, as compared to the ionized gas.

  18. The H I content of extremely metal-deficient blue compact dwarf galaxies

    Science.gov (United States)

    Thuan, T. X.; Goehring, K. M.; Hibbard, J. E.; Izotov, Y. I.; Hunt, L. K.

    2016-09-01

    We have obtained new H I observations with the 100 m Green Bank Telescope (GBT) for a sample of 29 extremely metal-deficient star-forming Blue Compact Dwarf (BCD) galaxies, selected from the Sloan Digital Sky Survey spectral data base to be extremely metal-deficient (12 + log O/H ≤ 7.6). Neutral hydrogen was detected in 28 galaxies, a 97% detection rate. Combining the H I data with SDSS optical spectra for the BCD sample and adding complementary galaxy samples from the literature to extend the metallicity and mass ranges, we have studied how the H I content of a galaxy varies with various global galaxian properties. There is a clear trend of increasing gas mass fraction with decreasing metallicity, mass and luminosity. We obtain the relation M(H I)/Lg∝ L_g^{-0.3}, in agreement with previous studies based on samples with a smaller luminosity range. The median gas mass fraction fgas for the GBT sample is equal to 0.94 while the mean gas mass fraction is 0.90±0.15, with a lower limit of ˜0.65. The H I depletion time is independent of metallicity, with a large scatter around the median value of 3.4 Gyr. The ratio of the baryonic mass to the dynamical mass of the metal-deficient BCDs varies from 0.05 to 0.80, with a median value of ˜0.2. About 65% of the BCDs in our sample have an effective yield larger than the true yield, implying that the neutral gas envelope in BCDs is more metal-deficient by a factor of 1.5-20, as compared to the ionized gas.

  19. The Lyman alpha Reference Sample VI: Lyman alpha escape from the edge-on disk galaxy Mrk1486

    CERN Document Server

    Duval, Florent; Hayes, Matthew; Zackrisson, Erik; Verhamme, Anne; Orlitova, Ivana; Adamo, Angela; Guaita, Lucia; Melinder, Jens; Cannon, John M; Laursen, Peter; Rivera-Thorsen, Thoger; Herenz, E Christian; Gruyters, Pieter; Mas-Hesse, J Miguel; Kunth, Daniel; Sandberg, Andreas; Schaerer, Daniel; Mansson, Tore

    2015-01-01

    While numerical simulations suggest that the strength of the Lyman alpha (Lya) line of star-forming disk galaxies strongly depends on the inclination at which they are observed (i.e. from edge-on to face-on, we expect to see a change from an attenuated Lya line to a strong Lya emission line), recent observations with the Hubble space telescope (HST) have highlighted few low-redshift highly inclined (edge-on) disk galaxies that breaks this trend. We aim to understand how a strong Lya emission line is able to escape from one of those inclined disk galaxies, named Mrk1486 (z=0.0338). For that purpose we used a large set of HST imaging and spectroscopic data to investigate both the ISM structure and the dominant source of Lya radiation inside Mrk1486. Moreover, we used a 3D Monte Carlo Lya radiation transfer code to study the radiative transfer of Lya and UV continuum photons inside a 3D geometry of neutral hydrogen (HI) and dust that models the ISM structure at the galaxy center. The analysis of IFU Halpha spect...

  20. The HST/ACS Coma Cluster Survey. VIII. Barred Disk Galaxies in the Core of the Coma Cluster

    CERN Document Server

    Marinova, Irina; Weinzirl, Tim; Erwin, Peter; Trentham, Neil; Ferguson, Henry C; Hammer, Derek; Brok, Mark den; Graham, Alister W; Carter, David; Balcells, Marc; Goudfrooij, Paul; Guzman, Rafael; Hoyos, Carlos; Mobasher, Bahram; Mouhcine, Mustapha; Peletier, Reynier F; Peng, Eric; Kleijn, Gijs Verdoes

    2012-01-01

    (ABRIDGED) We use high resolution (~0.1") F814W ACS images from the HST ACS Treasury survey of the Coma cluster at z~0.02 to study bars in massive disk galaxies (S0s), and in dwarf galaxies in the Coma core. Our study helps constrain the evolution of bars and disks in dense environments and provides a comparison point for studies in lower density environments and at higher redshifts. (1) We characterize the fraction and properties of bars in a sample of 32 bright (M_V 10^9.5 M_sun) S0 galaxies, which dominate the population of massive disk galaxies in the Coma core. Measuring the S0 bar fraction must be handled carefully, as the results depend on the method used: the bar fraction for bright S0s in the Coma core is 50%+/-11%, 65%+/-11%, and 60%+/-11% for three methods of bar detection: strict ellipse fit criteria, relaxed ellipse fit criteria, and visual classification. (2) We compare the S0 bar fraction across different environments (Coma core, A901/902, Virgo). We find that the bar fraction among bright S0 ...

  1. The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts

    CERN Document Server

    Mandelbaum, Rachel; Bridle, Sarah; Abdalla, Filipe B; Brough, Sarah; Colless, Matthew; Couch, Warrick; Croom, Scott; Davis, Tamara; Drinkwater, Michael J; Forster, Karl; Glazebrook, Karl; Jelliffe, Ben; Jurek, Russell J; Li, Tornado; Madore, Barry; Martin, Chris; Pimbblet, Kevin; Poole, Gregory B; Pracy, Michael; Sharp, Rob; Wisnioski, Emily; Woods, David; Wyder, Ted

    2009-01-01

    Correlations between the intrinsic shapes of galaxy pairs, and between the intrinsic shapes of galaxies and the large-scale density field, may be induced by tidal fields. These correlations, which have been detected at low redshifts (z<0.35) for bright red galaxies in the Sloan Digital Sky Survey (SDSS), and for which upper limits exist for blue galaxies at z~0.1, provide a window into galaxy formation and evolution, and are also an important contaminant for current and future weak lensing surveys. Measurements of these alignments at intermediate redshifts (z~0.6) that are more relevant for cosmic shear observations are very important for understanding the origin and redshift evolution of these alignments, and for minimising their impact on weak lensing measurements. We present the first such intermediate-redshift measurement for blue galaxies, using galaxy shape measurements from SDSS and spectroscopic redshifts from the WiggleZ Dark Energy Survey. Our null detection allows us to place upper limits on the...

  2. Dark matter in disk galaxies I: a Markov Chain Monte Carlo method and application to DDO 154

    CERN Document Server

    Hague, Peter R

    2013-01-01

    We present a new method to constrain the dark matter halo density profiles of disk galaxies. Our algorithm employs a Markov Chain Monte Carlo (MCMC) approach to explore the parameter space of a general family of dark matter profiles. We improve upon previous analyses by considering a wider range of halo profiles and by explicitly identifying cases in which the data are insufficient to break the degeneracies between the model parameters. We demonstrate the robustness of our algorithm using artificial data sets and show that reliable estimates of the halo density profile can be obtained from data of comparable quality to those currently available for low surface brightness (LSB) galaxies. We present our results in terms of physical quantities which are constrained by the data, and find that the logarithmic slope of the halo density profile at the radius of the innermost data point of a measured rotation curve can be strongly constrained in LSB galaxies. High surface brightness galaxies require additional inform...

  3. On the origin of the Schechter-like mass function of young star clusters in disk galaxies

    CERN Document Server

    Lieberz, Patrick

    2016-01-01

    The mass function of freshly formed star clusters is empirically often described as a power law. However the cluster mass function of populations of young clusters over the scale of a galaxy has been found to be described by a Schechter-function. Here we address this apparent discrepancy. We assume that in an annulus of an isolated self- regulated radially-exponential axially-symmetric disk galaxy, the local mass function of very young (embedded) clusters is a power law with an upper mass limit which depends on the local star formation rate density. Radial integration of this mass function yields a galaxy-wide embedded cluster mass function. This integrated embedded cluster mass function has a Schechter-type form, which results from the addition of many low mass clusters forming at all galactocentric distances and rarer massive clusters only forming close to the center of the galaxy.

  4. Origins of the thick disk of the galaxy as traced by metal-poor stars selected from RAVE

    Directory of Open Access Journals (Sweden)

    Ruchti G.R.

    2012-02-01

    Full Text Available Models of the formation of the thick disk of the Milky Way Galaxy make specific predictions about the chemical abundance properties of the metal-weak (and oldest stellar population in the thick disk. We have undertaken the study of the elemental abundances and kinematic properties of a sample of 319 candidate metal-poor thick-disk stars selected from the RAVE spectroscopic survey of bright stars. Our aim is to differentiate among the present scenarios of the formation of the thick disk. In this study, we measured the abundances of several alpha-elements and found that the thick-disk [alpha/Fe] ratios are enhanced, implying that enrichment proceeded by purely core-collapse supernovae. Further, the sample probes distances ranging out to about 2 kpc from the Sun, allowing for the investigation of the gradients in the thick disk. I will discuss the results from these investigations and how they compare to the predictions made by present models of the formation of the thick disk.

  5. Amazing Andromeda Galaxy

    Science.gov (United States)

    2006-01-01

    The many 'personalities' of our great galactic neighbor, the Andromeda galaxy, are exposed in this new composite image from NASA's Galaxy Evolution Explorer and the Spitzer Space Telescope. The wide, ultraviolet eyes of Galaxy Evolution Explorer reveal Andromeda's 'fiery' nature -- hotter regions brimming with young and old stars. In contrast, Spitzer's super-sensitive infrared eyes show Andromeda's relatively 'cool' side, which includes embryonic stars hidden in their dusty cocoons. Galaxy Evolution Explorer detected young, hot, high-mass stars, which are represented in blue, while populations of relatively older stars are shown as green dots. The bright yellow spot at the galaxy's center depicts a particularly dense population of old stars. Swaths of red in the galaxy's disk indicate areas where Spitzer found cool, dusty regions where stars are forming. These stars are still shrouded by the cosmic clouds of dust and gas that collapsed to form them. Together, Galaxy Evolution Explorer and Spitzer complete the picture of Andromeda's swirling spiral arms. Hints of pinkish purple depict regions where the galaxy's populations of hot, high-mass stars and cooler, dust-enshrouded stars co-exist. Located 2.5 million light-years away, the Andromeda is our largest nearby galactic neighbor. The galaxy's entire disk spans about 260,000 light-years, which means that a light beam would take 260,000 years to travel from one end of the galaxy to the other. By comparison, our Milky Way galaxy's disk is about 100,000 light-years across. This image is a false color composite comprised of data from Galaxy Evolution Explorer's far-ultraviolet detector (blue), near-ultraviolet detector (green), and Spitzer's multiband imaging photometer at 24 microns (red).

  6. No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS / 3D-HST

    CERN Document Server

    Trump, Jonathan R; Juneau, Stephanie; Weiner, Benjamin J; Luo, Bin; Brammer, Gabriel B; Bell, Eric F; Brandt, W Niel; Dekel, Avishai; Guo, Yicheng; Hopkins, Philip F; Koo, David C; Kocevski, Dale D; McIntosh, Daniel H; Momcheva, Ivelina; Faber, S M; Ferguson, Henry C; Grogin, Norman A; Kartaltepe, Jeyhan; Koekemoer, Anton M; Lotz, Jennifer; Maseda, Michael; Mozena, Mark; Nandra, Kirpal; Rosario, David J; Zeimann, Gregory R

    2014-01-01

    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that, despite being being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z~2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z~2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratio...

  7. Disk galaxy scaling relations at intermediate redshifts. I. The Tully-Fisher and velocity-size relations

    Science.gov (United States)

    Böhm, Asmus; Ziegler, Bodo L.

    2016-07-01

    Aims: Galaxy scaling relations such as the Tully-Fisher relation (between the maximum rotation velocity Vmax and luminosity) and the velocity-size relation (between Vmax and the disk scale length) are powerful tools to quantify the evolution of disk galaxies with cosmic time. Methods: We took spatially resolved slit spectra of 261 field disk galaxies at redshifts up to z ≈ 1 using the FORS instruments of the ESO Very Large Telescope. The targets were selected from the FORS Deep Field and William Herschel Deep Field. Our spectroscopy was complemented with HST/ACS imaging in the F814W filter. We analyzed the ionized gas kinematics by extracting rotation curves from the two-dimensional spectra. Taking into account all geometrical, observational, and instrumental effects, these rotation curves were used to derive the intrinsic Vmax. Results: Neglecting galaxies with disturbed kinematics or insufficient spatial rotation curve extent, Vmax was reliably determined for 124 galaxies covering redshifts 0.05 gas and/or small satellites. From scrutinizing the combined evolution in luminosity and size, we find that the galaxies that show the strongest evolution toward smaller sizes at z ≈ 1 are not those that feature the strongest evolution in luminosity, and vice versa. Based on observations with the European Southern Observatory Very Large Telescope (ESO-VLT), observing run IDs 65.O-0049, 66.A-0547, 68.A-0013, 69.B-0278B, 70.B-0251A and 081.B-0107A.The full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A64

  8. The HI and Ionized Gas Disk of the Seyfert Galaxy NGC 1144 = Arp 118 A Violently Interacting Galaxy with Peculiar Kinematics

    CERN Document Server

    Bransford, M A; McCain, C F; Freeman, K C

    1999-01-01

    We present observations of the distribution and kinematics of neutral and ionized gas in NGC 1144, a galaxy that forms part of the Arp 118 system. Ionized gas is present over a huge spread in velocity (1100 km/s) in the disk of NGC 1144, but HI emission is detected over only 1/3 of this velocity range, in an area that corresponds to the NW half of the disk. In the nuclear region of NGC 1144, a jump in velocity in the ionized gas component of 600 km/s is observed. Faint, narrow HI absorption lines are also detected against radio sources in the SE part of the disk of NGC 1144, which includes regions of massive star formation and a Seyfert nucleus. The peculiar HI distribution, which is concentrated in the NW disk, seems to be the inverse of the molecular distribution which is concentrated in the SE disk. Although this may partly be the result of the destruction of HI clouds in the SE disk, there is circumstantial evidence that the entire HI emission spectrum of NGC 1144 is affected by a deep nuclear absorption ...

  9. The ACS LCID Project. VII. The Blue Stragglers Population in the Isolated dSph Galaxies Cetus and Tucana

    NARCIS (Netherlands)

    Monelli, M.; Cassisi, S.; Mapelli, M.; Bernard, E. J.; Aparicio, A.; Skillman, E. D.; Stetson, P. B.; Gallart, C.; Hidalgo, S. L.; Mayer, L.; Tolstoy, E.

    2012-01-01

    We present the first investigation of the Blue Straggler star (BSS) population in two isolated dwarf spheroidal galaxies of the Local Group, Cetus and Tucana. Deep Hubble Space Telescope/Advanced Camera for Surveys photometry allowed us to identify samples of 940 and 1214 candidates, respectively. T

  10. The ACS LCID Project : VII. The Blue Stragglers Population in the Isolated dSph Galaxies Cetus and Tucana

    NARCIS (Netherlands)

    Monelli, M.; Cassisi, S.; Mapelli, M.; Bernard, E. J.; Aparicio, A.; Skillman, E. D.; Stetson, P. B.; Gallart, C.; Hidalgo, S. L.; Mayer, L.; Tolstoy, E.

    2012-01-01

    We present the first investigation of the Blue Straggler star (BSS) population in two isolated dwarf spheroidal galaxies of the Local Group, Cetus and Tucana. Deep Hubble Space Telescope/Advanced Camera for Surveys photometry allowed us to identify samples of 940 and 1214 candidates, respectively. T

  11. Monsters in the Dark: Predictions for Luminous Galaxies in the Early Universe from the BlueTides Simulation

    CERN Document Server

    Waters, Dacen; Di Matteo, Tiziana; Feng, Yu; Croft, Ruper; Nagai, Daisuke

    2016-01-01

    Using deep Hubble and Spitzer observations Oesch et al. (2016) have identified a bright ($M_{\\rm UV}\\approx -22$) star forming galaxy candidate at $z \\approx 11$. The presence of GN-$z11$ implies a number density $\\sim 10^{-6}\\,{\\rm Mpc^{-3}}$, roughly an order of magnitude higher than the expected value based on extrapolations from lower redshift. Using the unprecedented volume and high resolution of the BlueTides cosmological hydrodynamical simulation, we study the population of luminous rare objects at $z > 10$. The luminosity function in BlueTides implies an enhanced number of massive galaxies, consistent with the observation of GN-$z11$. We find about 30 galaxies at $M_{\\rm UV}\\approx -22$ at $z = 11$ in the BlueTides volume, including a few objects about 1.5 magnitudes brighter. The probability of observing GN-$z11$ in the volume probed by Oesch et al. (2016) is $\\sim 13$ per cent. The predicted properties of the rare bright galaxies at $z = 11$ in BlueTides closely match those inferred from the observa...

  12. Stellar mass distribution of S4G disk galaxies and signatures of bar-induced secular evolution

    Science.gov (United States)

    Díaz-García, S.; Salo, H.; Laurikainen, E.

    2016-12-01

    Context. Models of galaxy formation in a cosmological framework need to be tested against observational constraints, such as the average stellar density profiles (and their dispersion) as a function of fundamental galaxy properties (e.g. the total stellar mass). Simulation models predict that the torques produced by stellar bars efficiently redistribute the stellar and gaseous material inside the disk, pushing it outwards or inwards depending on whether it is beyond or inside the bar corotation resonance radius. Bars themselves are expected to evolve, getting longer and narrower as they trap particles from the disk and slow down their rotation speed. Aims: We use 3.6 μm photometry from the Spitzer Survey of Stellar Structure in Galaxies (S4G) to trace the stellar distribution in nearby disk galaxies (z ≈ 0) with total stellar masses 108.5 ≲ M∗/M⊙ ≲ 1011 and mid-IR Hubble types - 3 ≤ T ≤ 10. We characterize the stellar density profiles (Σ∗), the stellar contribution to the rotation curves (V3.6 μm), and the m = 2 Fourier amplitudes (A2) as a function of M∗ and T. We also describe the typical shapes and strengths of stellar bars in the S4G sample and link their properties to the total stellar mass and morphology of their host galaxy. Methods: For 1154 S4G galaxies with disk inclinations lower than 65°, we perform a Fourier decomposition and rescale their images to a common frame determined by the size in physical units, by their disk scalelength, and for 748 barred galaxies by both the length and orientation of their bars. We stack the resized density profiles and images to obtain statistically representative average stellar disks and bars in bins of M∗ and T. Based on the radial force profiles of individual galaxies we calculate the mean stellar contribution to the circular velocity. We also calculate average A2 profiles, where the radius is normalized to R25.5. Furthermore, we infer the gravitational potentials from the synthetic bars to

  13. The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

    CERN Document Server

    Kuo, C Y; Condon, J J; Impellizzeri, C M V; Lo, K Y; Zaw, I; Schenker, M; Henkel, C; Reid, M J; Greene, J E

    2010-01-01

    Observations of H$_2$O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry (VLBI) images and kinematics of water maser emission in six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388, NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central $\\sim0.3$ pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 and 60 $\\times 10^{10} M_{\\odot}$~pc$^{-3}$. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominant...

  14. The Near-infrared S0 Survey III: Morphology of 15 Southern Early-type Disk Galaxies

    CERN Document Server

    Laurikainen, E; Buta, R; Knapen, J; Speltincx, T; Block, D

    2006-01-01

    Structural analysis has been performed for a sample of 15 Southern early-type disk galaxies, mainly S0s, using high resolution $K_s$-band images. The galaxies are mostly barred and many of them show multiple structures including bars and ovals, typical for S0s. The new images are of sufficient quality to reveal new detail on the morphology of the galaxies. For example, we report a hitherto undetected nuclear ring in NGC 1387, a nuclear bar in NGC 1326, and in the residual image also a weak primary bar in NGC 1317. For the galaxies we (1) measure the radial profiles of the orientation parameters derived from the elliptical isophotes, (2) apply Fourier methods for calculating tangential forces, and particularly, (3) apply structural decomposition methods. For galaxies with multiple structures a 2-dimensional method is found to be superior to a 1-dimensional method, but only if in addition to the bulge and the disk, at least one other component is taken into account. {\\it We find strong evidence of pseudo-bulges...

  15. The growth of disks and bulges during hierarchical galaxy formation. II: metallicity, stellar populations and dynamical evolution

    CERN Document Server

    Tonini, Chiara; Wyithe, J Stuart B; Croton, Darren J

    2016-01-01

    We investigate the properties of the stellar populations of model galaxies, using the new semi-analytic model presented in Tonini et al. (2016a). This new model follows the angular momentum evolution of gas and stars, providing the base for a new star formation recipe, and treatment of the effects of mergers that depends on the central galaxy dynamical structure. We find that the new recipes have the effect of boosting the efficiency of the baryonic cycle in producing and recycling metals, as well as preventing minor mergers from diluting the metallicity of bulges and ellipticals. The model reproduces the stellar mass - stellar metallicity relation for galaxies above 1e10 solar masses, including Brightest Cluster Galaxies. Model disks, galaxies dominated by instability-driven components, and merger-driven objects each stem from different evolutionary channels. These model galaxies therefore occupy different loci in the galaxy mass - size relation, which we find to be in accord with the Atlas 3D classification...

  16. Powerful red-green-blue laser source pumped with a mode-locked thin disk laser.

    Science.gov (United States)

    Brunner, Felix; Innerhofer, Edith; Marchese, Sergio V; Südmeyer, Thomas; Paschotta, Rüdiger; Usami, Takeshi; Ito, Hiromasa; Kurimura, Sunao; Kitamura, Kenji; Arisholm, Gunnar; Keller, Ursula

    2004-08-15

    We present a red-green-blue laser source with average powers of 8 W in the red, 23 W in the green, and 10.1 W in the blue. The entire pump power for the nonlinear conversion stages is provided by a single laser oscillator without any amplifier stages. Our system does not require any synchronized cavities, and all nonlinear crystals except one are critically phase matched at room temperature.

  17. The History of Star Formation in Galaxy Disks in the Local Volume as Measured by the ACS Nearby Galaxy Survey Treasury

    CERN Document Server

    Williams, Benjamin F; Johnson, L C; Weisz, Daniel R; Seth, Anil C; Dolphin, Andrew; Gilbert, Karoline M; Skillman, Evan; Rosema, Keith; Gogarten, Stephanie M; Holtzman, Jon; de Jong, Roelof S

    2011-01-01

    We present a measurement of the age distribution of stars residing in spiral disks and dwarf galaxies. We derive a complete star formation history of the ~140 Mpc^3 covered by the volume-limited sample of galaxies in the Advanced Camera for Surveys (ACS) Nearby Galaxy Survey Treasury (ANGST). The total star formation rate density history is dominated by the large spirals in the volume, although the sample consists mainly of dwarf galaxies. Our measurement shows a factor of ~3 drop at z~2, in approximate agreement with results from other measurement techniques. While our results show that the overall star formation rate density has decreased since z~1, the measured rates during this epoch are higher than those obtained from other measurement techniques. This enhanced recent star formation rate appears to be largely due to an increase in the fraction of star formation contained in low-mass disks at recent times. Finally, our results indicate that despite the differences at recent times, the epoch of formation o...

  18. VII Zw 403: HI Structure in a Blue Compact Dwarf Galaxy

    CERN Document Server

    Simpson, Caroline E; Nordgren, Tyler E; Brinks, Elias; Elmegreen, Bruce G; Ashley, Trisha; Lynds, Roger; McIntyre, Vince J; O'Neil, Earl J; Östlin, Göran; Westpfahl, David J; Wilcots, Eric M

    2011-01-01

    We present optical (UBVJ), ultraviolet (FUV, NUV), and high resolution atomic hydrogen (HI) observations of the nearby blue compact dwarf (BCD), VII Zw 403. We find that VII Zw 403 has a relatively high HI mass-to-light ratio for a BCD. The rotation velocity is nominally 10-15 km/s, but rises to ~20 km/s after correction for the ~8-10 km/s random motions present in the gas. The velocity field is complex; including a variation in the position angle of the major axis going from the NE to the SW parts of the galaxy. Our high resolution HI maps reveal structure in the central gas, including a large, low-density HI depression or hole between the southern and northern halves of the galaxy, coincident with an unresolved x-ray source. Although interactions have been proposed as the triggering mechanism for the vigorous star formation occurring in BCDs, VII Zw 403 does not seem to have been tidally triggered by an external interaction, as we have found no nearby possible perturbers. It also doesn't appear to fall in t...

  19. 3D Spectroscopy of Local Luminous Compact Blue Galaxies: Kinematics of NGC 7673

    CERN Document Server

    Pérez-Gallego, J; Castillo-Morales, A; Castander, F J; Gallego, J; Garland, C A; Gruel, N; Pisano, D J; Sánchez, S F; Zamorano, J

    2009-01-01

    The kinematic properties of the ionized gas of local Luminous Compact Blue Galaxy (LCBG) NGC 7673 are presented using three dimensional data taken with the PPAK integral field unit at the 3.5-m telescope in the Centro Astron\\'omico Hispano Alem\\'an. Our data reveal an asymmetric rotating velocity field with a peak to peak difference of 60 km s$^{-1}$. The kinematic centre is found to be at the position of a central velocity width maximum ($\\sigma=54\\pm1$ km s$^{-1}$), which is consistent with the position of the luminosity-weighted centroid of the entire galaxy. The position angle of the minor rotation axis is 168$^{\\circ}$ as measured from the orientation of the velocity field contours. At least two decoupled kinematic components are found. The first one is compact and coincides with the position of the second most active star formation region (clump B). The second one is extended and does not have a clear optical counterpart. No evidence of active galactic nuclei activity or supernovae galactic winds poweri...

  20. The Properties of the Circumgalactic Medium in Red and Blue Galaxies: Results from the COS-GASS+COS-Halos Surveys

    Science.gov (United States)

    Borthakur, Sanchayeeta; Heckman, Timothy; Tumlinson, Jason; Bordoloi, Rongmon; Kauffmann, Guinevere; Catinella, Barbara; Schiminovich, David; Davé, Romeel; Moran, Sean M.; Saintonge, Amelie

    2016-12-01

    We use the combined data from the COS-GASS and COS-Halos surveys to characterize the Circum-Galactic Medium (CGM) surrounding typical low-redshift galaxies in the mass range {M}* ˜ {10}9.5-11.5 {M}⊙ , and over a range of impact parameters extending to just beyond the halo virial radius (R vir). We find the radial scale length of the distributions of the equivalent widths of the Lyα and Si iii absorbers to be ˜1 and ˜0.4 R vir, respectively. The radial distribution of equivalent widths is relatively uniform for the blue galaxies, but highly patchy (i.e., it has a low covering fraction) for the red galaxies. We also find that the Lyα and Si iii equivalent widths show significant positive correlations with the specific star formation rate (sSFR) of the galaxy. We find a surprising lack of correlations between the halo mass (virial velocity) and either the velocity dispersions or velocity offsets of the Lyα lines. The ratio of the velocity offset to the velocity dispersion for the Lyα absorbers has a mean value of ˜4, suggesting that a given line of sight is intersecting a dynamically coherent structure in the CGM, rather than a sea of orbiting clouds. The kinematic properties of the CGM are similar in the blue and red galaxies, although we find that a significantly larger fraction of the blue galaxies have large Lyα velocity offsets (>200 km s-1). We show that—if the CGM clouds represent future fuel for star formation—our new results could imply a large drop in the sSFR across the galaxy mass-range we probe.

  1. The DiskMass Survey. VI. Gas and stellar kinematics in spiral galaxies from PPak integral-field spectroscopy

    CERN Document Server

    Martinsson, Thomas P K; Westfall, Kyle B; Bershady, Matthew A; Schechtman-Rook, Andrew; Andersen, David R; Swaters, Rob A

    2013-01-01

    We present ionized-gas (OIII) and stellar kinematics (velocities and velocity dispersions) for 30 nearly face-on spiral galaxies out to as much as three disk scale lengths (h_R). These data have been derived from PPak IFU spectroscopy (4980-5370A), observed at a mean resolution of R=7700 (sigma_inst=17km/s). These data are a fundamental product of our survey and will be used in companion papers to, e.g., derive the detailed (baryonic+dark) mass budget of each galaxy in our sample. Our presentation provides a comprehensive description of the observing strategy, data reduction, and analysis. Along with a clear presentation of the data, we demonstrate: (1) The OIII and stellar rotation curves exhibit a clear signature of asymmetric drift with a rotation difference that is 11% of the maximum rotation speed of the galaxy disk, comparable to measurements in the solar neighborhood in the Milky Way. (2) The e-folding length of the stellar velocity dispersion is two times h_R on average, as expected for a disk with a ...

  2. The Atomic to Molecular Transition and its Relation to the Scaling Properties of Galaxy Disks in the Local Universe

    CERN Document Server

    Fu, Jian; Kauffmann, Guinevere; Krumholz, Mark R

    2010-01-01

    We extend existing semi-analytic models of galaxy formation to track atomic and molecular gas in disk galaxies. Simple recipes for processes such as cooling, star formation, supernova feedback, and chemical enrichment of the stars and gas are grafted on to dark matter halo merger trees derived from the Millennium Simulation. Each galactic disk is represented by a series of concentric rings. We assume that surface density profile of infalling gas in a dark matter halo is exponential, with scale radius r_d that is proportional to the virial radius of the halo times its spin parameter $\\lambda$. As the dark matter haloes grow through mergers and accretion, disk galaxies assemble from the inside out. We include two simple prescriptions for molecular gas formation processes in our models: one is based on the analytic calculations by Krumholz, McKee & Tumlinson (2008), and the other is a prescription where the H_2 fraction is determined by the kinematic pressure of the ISM. Motivated by the observational result...

  3. Chandra survey of nearby highly inclined disk galaxies -- IV: New insights into the working of stellar feedback

    CERN Document Server

    Wang, Q Daniel; Jiang, Xiaochuan; Fang, Taotao

    2015-01-01

    Galaxy evolution is regulated by the interplay between galactic disks and their surrounding medium. We study this interplay by examining how the galactic coronal emission efficiency of stellar feedback depends on the (surface and specific) star formation rates (SFRs) and other parameters for a sample of 52 Chandra-observed nearby highly inclined disk galaxies. We first measure the star forming galactic disk sizes, as well as the SFRs of these galaxies, using data from the Wide-Field Infrared Survey Explorer, and then show that 1) the specific 0.5-2~keV luminosity of the coronal emission correlates with the specific SFR in a {\\sl sub-linear} fashion: on average, $L_X/L_K \\propto (SFR/M_*)^{\\Gamma}$ with $\\Gamma =0.29\\pm0.12$; 2) the efficiency of the emission $ L_X/SFR$ decreases with increasing surface SFR ($I_{SFR}$; $\\Gamma = -0.44\\pm0.12$); and 3) the characteristic temperature of the X-ray-emitting plasma weakly correlates with $I_{SFR}$ ($\\Gamma = 0.08\\pm0.04$). These results, somewhat surprising and ant...

  4. Surface brightness and color distributions in blue compact dwarf galaxies. I - Haro 2, an extreme example of a star-forming young elliptical galaxy

    Science.gov (United States)

    Loose, Hans-Hermann; Thuan, Trinh X.

    1986-01-01

    The first results of a large-scale program to study the morphology and structure of blue compact dwarf galaxies from CCD observations are presented. The observations and reduction procedures are described, and surface brightness and color profiles are shown. The results are used to discuss the morphological type of Haro 2 and its stellar populations. It is found that Haro 2 appears to be an extreme example of an elliptical galaxy undergoing intense star formation in its central regions, and that the oldest stars it contains were made only about four million yr ago. The 'missing' mass problem of Haro 2 is also discussed.

  5. Transition of an X-ray binary to the hard ultraluminous state in the blue compact dwarf galaxy VII Zw 403

    CERN Document Server

    Brorby, Matthew; Feng, Hua

    2015-01-01

    We examine the X-ray spectra of VII Zw 403, a nearby low-metallicity blue compact dwarf (BCD) galaxy. The galaxy has been observed to contain an X-ray source, likely a high mass X-ray binary (HMXB), with a luminosity of 1.3-23x10^38 erg s^-1 in the 0.3-8 keV energy range. A new Suzaku observation shows a transition to a luminosity of 1.7x10^40 erg s^-1 [0.3-8 keV], higher by a factor of 7-130. The spectra from the high flux state are hard, best described by a disk plus Comptonization model, and exhibit curvature at energies above 5 keV. This is consistent with many high-quality ultraluminous X-ray source spectra which have been interpreted as stellar mass black holes (StMBH) accreting at super-Eddington rates. However, this lies in contrast to another HMXB in a low-metallicity BCD, I Zw 18, that exhibits a soft spectrum at high flux, similar to Galactic black hole binaries and has been interpreted as a possible intermediate mass black hole. Determining the spectral properties of HMXBs in BCDs has important im...

  6. Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions

    CERN Document Server

    Tasker, Elizabeth J

    2008-01-01

    We investigate the formation and evolution of giant molecular clouds (GMCs) in a Milky-Way-like disk galaxy with a flat rotation curve. We perform a series of 3D adaptive mesh refinement (AMR) numerical simulations that follow both the global evolution on scales of ~20kpc and resolve down to scales ~=100cm^-3 and track the evolution of individual clouds as they orbit through the galaxy from their birth to their eventual destruction via merger or via destructive collision with another cloud. After ~140Myr a large fraction of the gas in the disk has fragmented in clouds, with typical masses ~10^6Msun, similar to Galactic GMCs. The disk settles into a quasi steady state in which gravitational scattering of clouds keeps the disk near the threshold of global gravitational instability. The cloud collision time is found to be a small fraction, ~1/5, of the orbital time, and this is an efficient mechanism to inject turbulence into the clouds. This keeps the clouds only moderately gravitationally bound, with virial pa...

  7. The ACS LCID project VII: the blue stragglers population in the isolated dSph galaxies Cetus and Tucana

    CERN Document Server

    Monelli, M; Mapelli, M; Bernard, E J; Aparicio, A; Skillman, E D; Stetson, P B; Gallart, C; Hidalgo, S L; Mayer, L; Tolstoy, E

    2011-01-01

    We present the first investigation of the Blue Straggler star (BSS) population in two isolated dwarf spheroidal galaxies of the Local Group, Cetus and Tucana. Deep HST/ACS photometry allowed us to identify samples of 940 and 1214 candidates, respectively. The analysis of the star formation histories of the two galaxies suggests that both host a population of BSSs. Specifically, if the BSS candidates are interpreted as young main sequence stars, they do not conform to their galaxy's age-metallicity relationship. The analysis of the luminosity function and the radial distributions support this conclusion, and suggest a non-collisional mechanism for the BSS formation, from the evolution of primordial binaries. This scenario is also supported by the results of new dynamical simulations presented here. Both galaxies coincide with the relationship between the BSS frequency and the absolute visual magnitude Mv found by Momany et al (2007). If this relationship is confirmed by larger sample, then it could be a valuab...

  8. Chandra Survey of Nearby Highly-Inclined Disk Galaxies I: X-ray Measurements of Galactic Coronae

    CERN Document Server

    Li, Jiang-Tao

    2012-01-01

    We present a systematical analysis of the Chandra observations of 53 nearby highly-inclined (i>60 degree) disk galaxies to study the coronae around them. This sample covers a broad range of galaxy properties: e.g., about three orders of magnitude in the SFR and more than two orders of magnitude in the stellar mass. The Chandra observations of the diffuse soft X-ray emission from 20 of these galaxies are presented for the first time. The data are reduced in a uniform manner, including the excision/subtraction of both resolved and unresolved stellar contributions. Various coronal properties, such as the scale height and luminosity, are characterized for all the sample galaxies. For galaxies with high enough counting statistics, we also examine the thermal and chemical states of the coronal gas. We note on galaxies with distinct multi-wavelength characteristics which may affect the coronal properties. The uniformly processed images, spectra, and brightness profiles, as well as the inferred hot gas parameters, fo...

  9. Can Massive Gravity Explain the Mass Discrepancy - Acceleration Relation of Disk Galaxies?

    CERN Document Server

    Trippe, Sascha

    2013-01-01

    The empirical mass discrepancy-acceleration (MDA) relation of disk galaxies provides a key test for models of galactic dynamics. In terms of modified laws of gravity and/or inertia, the MDA relation quantifies the transition from Newtonian to modified dynamics at low centripetal accelerations a_c < 10^-10 m/s^2. As yet, neither dynamical models based on dark matter nor proposed modifications of the laws of gravity/inertia have predicted the functional form of the MDA relation. In this work, I revisit the MDA data and compare them to four different theoretical scaling laws. Three of these scaling laws are entirely empirical, the fourth one - the "simple mu" function of Modified Newtonian Dynamics - derives from a toy model of gravity based on massive gravitons (the "graviton picture"). All theoretical MDA relations comprise one free parameter of the dimension of an acceleration, Milgrom's constant a_M. I find that the "simple mu" function provides a good fit to the data free of notable systematic residuals ...

  10. Probing the Disk-jet Connection of the Radio Galaxy 3C120 Observed with Suzaku

    CERN Document Server

    Kataoka, J; Iwasawa, K; Markowitz, A G; Mushotzky, R F; Arimoto, M; Takahashi, T; Tsubuku, Y; Ushio, M; Watanabe, S; Gallo, L C; Madejski, G M; Terashima, Y; Isobe, N; Tashiro, M S; Kohmura, T; Kataoka, Jun; Reeves, James N.; Iwasawa, Kazushi; Markowitz, Alex G.; Mushotzky, Richard F.; Arimoto, Makoto; Takahashi, Tadayuki; Tsubuku, Yoshihiro; Ushio, Masayoshi; Watanabe, Shin; Gallo, Luigi C.; Madejski, Greg M.; Terashima, Yuichi; Isobe, Naoki; Tashiro, Makoto S.; Kohmura, Takayoshi

    2006-01-01

    Broad line radio galaxies (BLRGs) are a rare type of radio-loud AGN, in which the broad optical permitted emission lines have been detected in addition to the extended jet emission. Here we report on deep (40ksec x4) observations of the bright BLRG 3C~120 using Suzaku. The observations were spaced a week apart, and sample a range of continuum fluxes. An excellent broadband spectrum was obtained over two decades of frequency (0.6 to 50 keV) within each 40 ksec exposure. We clearly resolved the iron K emission line complex, finding that it consists of a narrow K_a core (sigma ~ 110 eV or an EW of 60 eV), a 6.9 keV line, and an underlying broad iron line. Our confirmation of the broad line contrasts with the XMM-Newton observation in 2003, where the broad line was not required. The most natural interpretation of the broad line is iron K line emission from a face-on accretion disk which is truncated at ~10 r_g. Above 10 keV, a relatively weak Compton hump was detected (reflection fraction of R ~ 0.6), superposed ...

  11. The Morphologies of Massive Galaxies at 1Disks

    CERN Document Server

    Bruce, V A; Cirasuolo, M; McLure, R J; Targett, T A; Bell, E F; Croton, D J; Dekel, A; Faber, S M; Ferguson, H C; Grogin, N A; Kocevski, D D; Koekemoer, A M; Koo, D C; Lai, K; Lotz, J M; McGrath, E J; Newman, J A; van der Wel, A

    2012-01-01

    We have used deep, HST, near-IR imaging to study the morphological properties of the most massive galaxies at high z, modelling the WFC3/IR H-band images of the ~200 galaxies in the CANDELS-UDS field with 1 10^11 M_sun. We have used both single-Sersic and bulge+disk models, have investigated the errors/biases introduced by uncertainties in the background and the PSF, and have obtained formally-acceptable model fits to >90% of the galaxies. Our results indicate that these massive galaxies at 1 2 the compact bulges display effective radii a factor ~4 smaller than local ellipticals of comparable mass. These trends appear to extend to the bulge components of disk-dominated galaxies, and vice versa. We also find that, while such massive galaxies at low z are bulge-dominated, at 1 2 they are mostly disk-dominated. The majority of the disk-dominated galaxies are actively forming stars, but this is also true for many of the bulge-dominated systems. Interestingly, however, while most of the quiescent galaxies are b...

  12. Star formation in galaxy mergers: ISM turbulence, dense gas excess, and scaling relations for disks and starbusts

    CERN Document Server

    Bournaud, Frederic; Chapon, Damien; Teyssier, Romain

    2010-01-01

    Galaxy interactions and mergers play a significant, but still debated and poorly understood role in the star formation history of galaxies. Numerical and theoretical models cannot yet explain the main properties of merger-induced starbursts, including their intensity and their spatial extent. Usually, the mechanism invoked in merger-induced starbursts is a global inflow of gas towards the central kpc, resulting in a nuclear starburst. We show here, using high-resolution AMR simulations and comparing to observations of the gas component in mergers, that the triggering of starbursts also results from increased ISM turbulence and velocity dispersions in interacting systems. This forms cold gas that are denser and more massive than in quiescent disk galaxies. The fraction of dense cold gas largely increases, modifying the global density distribution of these systems, and efficient star formation results. Because the starbursting activity is not just from a global compacting of the gas to higher average surface de...

  13. VizieR Online Data Catalog: Tully-Fisher relation in disk galaxies from SPARC (Lelli+, 2016)

    Science.gov (United States)

    Lelli, F.; McGaugh, S. S.; Schombert, J. M.

    2017-02-01

    This work is based on the Spitzer Photometry and Accurate Rotation Curves (SPARC) data set, presented in detail in Lelli et al. 2016 (Cat. J/AJ/152/157). In short, we collected more than 200 high-quality HI rotation curves of disk galaxies from previous compilations, large surveys, and individual studies. Subsequently, we searched the Spitzer archive for 3.6μm images of these galaxies. We found 173 objects with useful [3.6] data. For the sake of this study, we exclude starburst dwarf galaxies (eight objects from Lelli et al. 2014, Cat. J/A+A/566/A71, and Holmberg II from Swaters et al. 2009A&A...493..871S) because they have complex HI kinematics and are likely involved in recent interactions (Lelli et al. 2014MNRAS.445.1694L). This reduces our starting sample to 164 objects. (1 data file).

  14. The red and blue galaxy populations in the GOODS field: evidence for an excess of red dwarfs

    CERN Document Server

    Salimbeni, S; Menci, N; Castellano, M; Fontana, A; Grazian, A; Pentericci, L; Trevese, D; Cristiani, S; Nonino, M; Vanzella, E

    2007-01-01

    We study the evolution of the galaxy population up to z\\sim3 as a function of its colour properties. In particular, luminosity functions and luminosity densities have been derived as a function of redshift for the blue/late and red/early populations. We use data from the GOODS-MUSIC catalogue which have typical magnitude limits z<26 and Ks<23.5 for most of the sample. About 8% of the galaxies have spectroscopic redshifts; the remaining have well calibrated photometric redshifts derived from the extremely wide multi-wavelength coverage in 14 bands (from the U band to the Spitzer 8 \\mu m band). We have derived a catalogue of galaxies complete in rest-frame B-band, which has been divided in two subsamples according to their rest-frame U-V colour (or derived specific star formation rate, SSFR) properties. We confirm a bimodality in the U-V colour and SSFR of the galaxy sample up to z\\sim 3. This bimodality is used to compute the LFs of the blue/late and red/early subsamples. The LFs of the blue/late and tot...

  15. The B-Band Luminosity Function of Red and Blue Galaxies up to z=3.5

    CERN Document Server

    Giallongo, E; Menci, N; Zamorani, G; Fontana, A; Dickinson, M; Cristiani, S; Pozzetti, L

    2004-01-01

    We have explored the redshift evolution of the luminosity function of red and blue galaxies up to $z=3.5$. This was possible joining a deep I band composite galaxy sample, which includes the spectroscopic K20 sample and the HDFs samples, with the deep $H_{AB}=26$ and $K_{AB}=25$ samples derived from the deep NIR images of the Hubble Deep Fields North and South, respectively. About 30% of the sample has spectroscopic redshifts and the remaining fraction well-calibrated photometric redshifts. This allowed to select and measure galaxies in the rest-frame blue magnitude up to $z\\sim 3$ and to derive the redshift evolution of the B-band luminosity function of galaxies separated by their rest-frame $U-V$ color or specific (i.e. per unit mass) star-formation rate. The class separation was derived from passive evolutionary tracks or from their observed bimodal distributions. Both distributions appear bimodal at least up to $z\\sim 2$ and the locus of red/early galaxies is clearly identified up to these high redshifts....

  16. Aperture corrections for disk galaxy properties derived from the CALIFA survey. Balmer emission lines in spiral galaxies

    CERN Document Server

    Iglesias-Páramo, J; Galbany, L; Sánchez, S F; Rosales-Ortega, F F; Mast, D; García-Benito, R; Husemann, B; Aguerri, J A L; Alves, J; Bekeraité, S; Bland-Hawthorn, J; Catalán-Torrecilla, C; de Amorim, A L; de Lorenzo-Cáceres, A; Ellis, S; Falcón-Barroso, J; Flores, H; Florido, E; Gallazzi, A; Gomes, J M; Delgado, R M González; Haines, T; Hernández-Fernández, J D; Kehrig, C; López-Sánchez, A R; Lyubenova, M; Marino, R A; Mollá, M; Monreal-Ibero, A; Mourão, A; Papaderos, P; Sánchez-Blázquez, P; Spekkens, K; Stanishev, V; van de Ven, G; Walcher, C J; Wisotzki, L; Zibetti, S; Ziegler, B

    2013-01-01

    This work investigates the effect of the aperture size on derived galaxy properties for which we have spatially-resolved optical spectra. We focus on some indicators of star formation activity and dust attenuation for spiral galaxies that have been widely used in previous work on galaxy evolution. We have used 104 spiral galaxies from the CALIFA survey for which 2D spectroscopy with complete spatial coverage is available. From the 3D cubes we have derived growth curves of the most conspicuous Balmer emission lines (Halpha, Hbeta) for circular apertures of different radii centered at the galaxy's nucleus after removing the underlying stellar continuum. We find that the Halpha flux (f(Halpha)) growth curve follows a well defined sequence with aperture radius showing low dispersion around the median value. From this analysis, we derive aperture corrections for galaxies in different magnitude and redshift intervals. Once stellar absorption is properly accounted for, the f(Halpha)/f(Hbeta) ratio growth curve shows...

  17. The WiggleZ Dark Energy Survey: Cosmological neutrino mass constraint from blue high-redshift galaxies

    OpenAIRE

    Riemer-Sørensen, Signe; Blake, Chris; Parkinson, David; Davis, Tamara M.; Brough, Sarah; Colless, Matthew; Contreras, Carlos; Couch, Warrick; Croom, Scott; Croton, Darren; Drinkwater, Michael J.; Forster, Karl; Gilbank, David; Gladders, Mike; Glazebrook, Karl

    2011-01-01

    The absolute neutrino mass scale is currently unknown, but can be constrained from cosmology. The WiggleZ high redshift star-forming blue galaxy sample is less sensitive to systematics from non-linear structure formation, redshift-space distortions and galaxy bias than previous surveys. We obtain a upper limit on the sum of neutrino masses of 0.60eV (95% confidence) for WiggleZ+Wilkinson Microwave Anisotropy Probe. Combining with priors on the Hubble Parameter and the baryon acoustic oscillat...

  18. Star formation and the interstellar medium in low surface brightness galaxies III. Why they are blue, thin and poor in molecular gas

    NARCIS (Netherlands)

    Gerritsen, JPE; de Blok, WJG

    1999-01-01

    We present N-body simulations of Low Surface Brightness (LSB) galaxies and their Interstellar Medium to investigate the cause for their low star formation rates (SFR). Due to their massive halos, stellar disks of LSB galaxies are very stable and thin. Lack of dust makes the projected edge-on surface

  19. Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Simulating the Growth of a Disk Galaxy and its Supermassive Black Hole in a Cosmological Context

    Energy Technology Data Exchange (ETDEWEB)

    Levine, Robyn Deborah [Univ. of Colorado, Boulder, CO (United States)

    2008-01-01

    Supermassive black holes (SMBHs) are ubiquitous in the centers of galaxies. Their formation and subsequent evolution is inextricably linked to that of their host galaxies, and the study of galaxy formation is incomplete without the inclusion of SMBHs. The present work seeks to understand the growth and evolution of SMBHs through their interaction with the host galaxy and its environment. In the first part of the thesis (Chap. 2 and 3), we combine a simple semi-analytic model of outflows from active galactic nuclei (AGN) with a simulated dark matter density distribution to study the impact of SMBH feedback on cosmological scales. We find that constraints can be placed on the kinetic efficiency of such feedback using observations of the filling fraction of the Lyα forest. We also find that AGN feedback is energetic enough to redistribute baryons over cosmological distances, having potentially significant effects on the interpretation of cosmological data which are sensitive to the total matter density distribution (e.g. weak lensing). However, truly assessing the impact of AGN feedback in the universe necessitates large-dynamic range simulations with extensive treatment of baryonic physics to first model the fueling of SMBHs. In the second part of the thesis (Chap. 4-6) we use a hydrodynamic adaptive mesh refinement simulation to follow the growth and evolution of a typical disk galaxy hosting a SMBH, in a cosmological context. The simulation covers a dynamical range of 10 million allowing us to study the transport of matter and angular momentum from super-galactic scales all the way down to the outer edge of the accretion disk around the SMBH. Focusing our attention on the central few hundred parsecs of the galaxy, we find the presence of a cold, self-gravitating, molecular gas disk which is globally unstable. The global instabilities drive super-sonic turbulence, which maintains local stability and allows gas to fuel a SMBH without first fragmenting completely

  20. Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

    Science.gov (United States)

    Michtchenko, T. A.; Vieira, R. S. S.; Barros, D. A.; Lépine, J. R. D.

    2017-01-01

    Context. Resonances in the stellar orbital motion under perturbations from the spiral arm structure can play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (in the context of nearly circular orbits), but is not suitable in general. Aims: We expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped groove profiles without any restriction on the stellar orbital configurations, and we expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes of initial conditions are constructed numerically in order to characterize the phase-space structure and identify the precise location of the co-rotation and Lindblad resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion. Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach. We generalize the concept of Lindblad resonances and extend it to cases of resonant orbits with large radial excursions, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters (SSP) may evolve in dynamically distinct regions, either inside the stable co-rotation resonance or in a chaotic zone. Conclusions: Our approach contributes to quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a

  1. The properties of the Malin 1 galaxy giant disk. A panchromatic view from the NGVS and GUViCS surveys

    Science.gov (United States)

    Boissier, S.; Boselli, A.; Ferrarese, L.; Côté, P.; Roehlly, Y.; Gwyn, S. D. J.; Cuillandre, J.-C.; Roediger, J.; Koda, J.; Muños Mateos, J. C.; Gil de Paz, A.; Madore, B. F.

    2016-10-01

    Context. Low surface brightness galaxies (LSBGs) represent a significant percentage of local galaxies but their formation and evolution remain elusive. They may hold crucial information for our understanding of many key issues (i.e., census of baryonic and dark matter, star formation in the low density regime, mass function). The most massive examples - the so called giant LSBGs - can be as massive as the Milky Way, but with this mass being distributed in a much larger disk. Aims: Malin 1 is an iconic giant LSBG - perhaps the largest disk galaxy known. We attempt to bring new insights on its structure and evolution on the basis of new images covering a wide range in wavelength. Methods: We have computed surface brightness profiles (and average surface brightnesses in 16 regions of interest), in six photometric bands (FUV, NUV, u, g, i, z). We compared these data to various models, testing a variety of assumptions concerning the formation and evolution of Malin 1. Results: We find that the surface brightness and color profiles can be reproduced by a long and quiet star-formation history due to the low surface density; no significant event, such as a collision, is necessary. Such quiet star formation across the giant disk is obtained in a disk model calibrated for the Milky Way, but with an angular momentum approximately 20 times larger. Signs of small variations of the star-formation history are indicated by the diversity of ages found when different regions within the galaxy are intercompared. Conclusions: For the first time, panchromatic images of Malin 1 are used to constrain the stellar populations and the history of this iconic example among giant LSBGs. Based on our model, the extreme disk of Malin 1 is found to have a long history of relatively low star formation (about 2 M⊙ yr-1). Our model allows us to make predictions on its stellar mass and metallicity. The Appendix images (FITS files) are available at the CDS via anonymous ftp to http

  2. U B V R I Photometry of Stellar Structures throughout the Disk of the Barred Galaxy NGC 3367

    CERN Document Server

    García-Barreto, J A; Moreno-Diaz, E; Bernal-Marin, T; Villarreal-Castillo, A L

    2007-01-01

    We report new detailed surface U, B, V, R, and I photometry of 81 stellar structures in the disk of the barred galaxy NGC 3367. The images show many different structures indicating that star formation is going on in the most part of the disk. NGC 3367 is known to have a very high concentration of molecular gas distribution in the central regions of the galaxy and bipolar synchrotron emission from the nucleus with two lobes (at 6 kpc) forming a triple structure similar to a radio galaxy. We have determined the U, B, V, R, and I magnitudes and U - B, B - V, U - V, and V - I colors for the central region (nucleus), a region which includes supernovae 2003 AA, and 79 star associations throughout NGC 3367. Estimation of ages of star associations is very difficult due to several factors, among them: filling factor, metallicity, spatial distribution of each structure and the fact that we estimated the magnitudes with a circular aperture of 16 pixels in diameter, equivalent to $6''.8\\sim1.4$ kpc. However, if the color...

  3. On the Influence of Minor Mergers on the Radial Abundance Gradient in Disks of Milky Way-like Galaxies

    CERN Document Server

    Zinchenko, Igor A; Grebel, Eva K; Pilyugin, Leonid S; Just, Andreas

    2015-01-01

    We investigate the influence of stellar migration caused by minor mergers (mass ratio from 1:70 to 1:8) on the radial distribution of chemical abundances in the disks of Milky Way-like galaxies during the last four Gyr. A GPU-based pure N-body tree-code model without hydrodynamics and star formation was used. We computed a large set of mergers with different initial satellite masses, positions, and orbital velocities. We find that there is no significant metallicity change at any radius of the primary galaxy in the case of accretion of a low-mass satellite of 10$^9$ M$_{\\odot}$ (mass ratio 1:70) except for the special case of prograde satellite motion in the disk plane of the host galaxy. The accretion of a satellite of a mass $\\gtrsim3\\times10^9$ M$_{\\odot}$ (mass ratio 1:23) results in an appreciable increase of the chemical abundances at galactocentric distances larger than $\\sim10$ kpc. The radial abundance gradient flattens in the range of galactocentric distances from 5 to 15 kpc in the case of a merger...

  4. The properties of the Malin 1 galaxy giant disk: A panchromatic view from the NGVS and GUViCS surveys

    CERN Document Server

    Boissier, S; Ferrarese, L; Cote, P; Roehlly, Y; Gwyn, S D J; Cuillandre, J -C; Roediger, J; Koda, J; Mateos, J C Munos; de Paz, A Gil; Madore, B F

    2016-01-01

    Low surface brightness galaxies (LSBGs) represent a significant percentage of local galaxies but their formation and evolution remain elusive. They may hold crucial information for our understanding of many key issues (i.e., census of baryonic and dark matter, star formation in the low density regime, mass function). The most massive examples - the so called giant LSBGs - can be as massive as the Milky Way, but with this mass being distributed in a much larger disk. Malin 1 is an iconic giant LSBG, perhaps the largest disk galaxy known. We attempt to bring new insights on its structure and evolution on the basis of new images covering a wide range in wavelength. We have computed surface brightness profiles (and average surface brightnesses in 16 regions of interest), in six photometric bands (FUV, NUV, u, g, i, z). We compared these data to various models, testing a variety of assumptions concerning the formation and evolution of Malin 1. We find that the surface brightness and color profiles can be reproduce...

  5. The metallicity evolution of blue compact dwarf galaxies from the intermediate redshift to the local Universe

    CERN Document Server

    Lian, Jianhui; Fang, Guanwen; Ye, Chengyun; Kong, Xu

    2016-01-01

    We present oxygen abundance measurements for 74 blue compact dwarf (BCD) galaxies in the redshift range in [0.2, 0.5] using the strong-line method. The spectra of these objects are taken using Hectospec on the Multiple Mirror Telescope (MMT). More than half of these BCDs had dust attenuation corrected using the Balmer decrement method. For comparison, we also selected a sample of 2023 local BCDs from the Sloan Digital Sky Survey (SDSS) database. Based on the local and intermediate-z BCD samples, we investigated the cosmic evo- lution of the metallicity, star-formation rate (SFR), and Dn (4000) index. Com- pared with local BCDs, the intermediate-z BCDs had a systematically higher R23 ratio but similar O32 ratio. Interestingly, no significant deviation in the mass-metallicity (MZ) relation was found between the intermediate-z and lo- cal BCDs. Besides the metallicity, the intermediate-z BCDs also exhibited an SFR distribution that was consistent with local BCDs, suggesting a weak de- pendence on redshift. The i...

  6. Constraints on Disks Models of The Big Blue Bump from UV/Optical/IR Observations

    CERN Document Server

    Antonucci, R

    1998-01-01

    Optical/UV observations provide many constraints on accretion disk models of AGN which aren't always appreciated by modelers of the X-ray emission (or sometimes even of the optical/UV emission). The spectral behavior at the Ly edge, the polarization, the continuum slopes and breaks, and the variability timescales and phasing all conflict with simple models and strongly constrain the more Baroque ones. Partial-covering absorbers and microlensing data suggest that the radiation is not released simply according to where the potential drop (modified by standard viscous transport) takes place. On the other hand, the orientation-based unified model is in accord with the K-\\alpha inclination distributions for the AGN spectral classes, basing the latter on the limited existing data and theoretical understanding.

  7. The dark and visible matter content of low surface brightness disk galaxies

    NARCIS (Netherlands)

    Blok, W. J. G. de; McGaugh, S. S.

    1997-01-01

    Abstract: We present mass models of a sample of 19 low surface brightness (LSB) galaxies and compare the properties of their constituent mass components with those of a sample of high surface brightness (HSB) galaxies.We find that LSB galaxies are dark matter dominated. Their halo parameters are onl

  8. Studies of Virgo cluster early-type dwarf galaxies with the SDSS: I. On the possible disk nature of bright early-type dwarfs

    CERN Document Server

    Lisker, T; Grebel, E K; Binggeli, Bruno; Grebel, Eva K.; Lisker, Thorsten

    2006-01-01

    We present a systematic search for disks in 476 Virgo cluster early-type dwarf (dE) galaxies. Disk features (spiral arms, edge-on disks, or bars) were identified by applying unsharp masks to a combined image from three bands (g, r, i), as well as by subtracting the axisymmetric light distribution of each galaxy from that image. 14 objects are unambiguous identifications of disks, 10 objects show 'probable disk' features, and 17 objects show 'possible disk' features. The number fraction of these galaxies, for which we introduce the term dEdi, reaches more than 50% at the bright end of the dE population, and decreases to less than 5% for magnitudes B>16. The luminosity function of our full dE sample can be explained by a superposition of dEdis and ordinary dEs, strongly suggesting that dEdis are a distinct type of galaxy. This is supported by the projected spatial distribution: dEdis show basically no clustering and roughly follow the spatial distribution of spirals and irregulars, whereas ordinary dEs are dist...

  9. X-shaped radio galaxies as observational evidence for the interaction of supermassive binary black holes and accretion disk at pc scale

    CERN Document Server

    Liu, F K

    2004-01-01

    A supermassive black hole binary may form during galaxy mergering. we investigate the interaction of the supermassive binary black holes (SMBBHs) and an accretion disk and show that the detected X-shaped structure in some FRII radio galaxies may be due to the interaction-realignment of inclined binary and accretion disk occurred within the pc scale of the galaxy center. We compare in detail the model and observations and show that the configuration is consistent very well with the observations of X-shaped radio sources. X-shaped radio feature form only in FRII radio sources due to the strong interaction between the binary and a standard disk, while the absence of X-shaped FRI radio galaxies is due to that the interaction between the binary and the radiatively inefficient accretion flow in FRI radio sources is negligible. It is suggested that the binary would keep misaligned with the outer disk for most of the life time of FRII radio galaxies and the orientation of jet in most FRII radio galaxies distributes r...

  10. Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: III. The Total Neutral Gas Disk

    CERN Document Server

    Nakanishi, Hiroyuki

    2015-01-01

    We present newly obtained three-dimensional gaseous maps of the Milky Way Galaxy; HI, H$_2$ and total-gas (HI plus H$_2$) maps, which were derived from the HI and $^{12}$CO($J=1$--0) survey data and rotation curves based on the kinematic distance. The HI and H$_2$ face-on maps show that the HI disk is extended to the radius of 15--20 kpc and its outskirt is asymmetric to the Galactic center, while most of the H$_2$ gas is distributed inside the solar circle. The total gas mass within radius 30 kpc amounts to $8.0\\times 10^9$ M$_\\odot$, 89\\% and 11\\% of which are HI and H$_2$, {respectively}. The vertical slices show that the outer HI disk is strongly warped and the inner HI and H$_2$ disks are corrugated. The total gas map is advantageous to trace spiral structure from the inner to outer disk. Spiral structures such as the Norma-Cygnus, the Perseus, the Sagittarius-Carina, the Scutum-Crux, and the Orion arms are more clearly traced in the total gas map than ever. All the spiral arms are well explained with lo...

  11. The Structure and Dynamical Evolution of the Stellar Disk of a Simulated Milky Way-Mass Galaxy

    CERN Document Server

    Ma, Xiangcheng; Wetzel, Andrew R; Kirby, Evan N; Angles-Alcazar, Daniel; Faucher-Giguere, Claude-Andre; Keres, Dusan; Quataert, Eliot

    2016-01-01

    We study the structure, age and metallicity gradients, and dynamical evolution using a cosmological zoom-in simulation of a Milky Way-mass galaxy from the Feedback in Realistic Environments project. In the simulation, stars older than 6 Gyr were formed in a chaotic, bursty mode and have the largest vertical scale heights (1.5-2.5 kpc) by z=0, while stars younger than 6 Gyr were formed in a relatively calm, stable disk. The vertical scale height increases with stellar age at all radii, because (1) stars that formed earlier were thicker "at birth", and (2) stars were kinematically heated to an even thicker distribution after formation. Stars of the same age are thicker in the outer disk than in the inner disk (flaring). These lead to positive vertical age gradients and negative radial age gradients. The radial metallicity gradient is neg- ative at the mid-plane, flattens at larger disk height |Z|, and turns positive above |Z|~1.5kpc. The vertical metallicity gradient is negative at all radii, but is steeper at ...

  12. Chandra survey of nearby highly inclined disk galaxies - IV. New insights into the working of stellar feedback

    Science.gov (United States)

    Wang, Q. Daniel; Li, Jiangtao; Jiang, Xiaochuan; Fang, Taotao

    2016-04-01

    Galaxy evolution is regulated by the interplay between galactic discs and their surrounding medium. We study this interplay by examining how the galactic coronal emission efficiency of stellar feedback depends on the (surface and specific) star formation rates (SFRs) and other parameters for a sample of 52 Chandra-observed nearby highly inclined disc galaxies. We first measure the star-forming galactic disc sizes, as well as the SFRs of these galaxies, using data from the Wide-Field Infrared Survey Explorer, and then show that (1) the specific 0.5-2 keV luminosity of the coronal emission correlates with the specific SFR in a sub-linear fashion: on average, LX/LK∝(SFR/M*)Γ with Γ = 0.29 ± 0.12; (2) the efficiency of the emission LX/SFR decreases with increasing surface SFR (ISFR; Γ = -0.44 ± 0.12); and (3) the characteristic temperature of the X-ray-emitting plasma weakly correlates with ISFR (Γ = 0.08 ± 0.04). These results, somewhat surprising and anti-intuitive, suggest that (i) the linear correlation between LX and SFR, as commonly presented, is largely due to the correlation of these two parameters with galaxy mass; (ii) much of the mechanical energy from stellar feedback likely drives global outflows with little X-ray cooling and with a mass-loading efficiency decreasing fast with increasing ISFR (Γ ≲ -0.5); (iii) these outflows heat and inflate the medium around the galactic disks of massive galaxies, reducing its radiative cooling rate, whereas for relatively low-mass galaxies, the energy in the outflows is probably dissipated in regions far away from the galactic discs.

  13. ACCRETION-INHIBITED STAR FORMATION IN THE WARM MOLECULAR DISK OF THE GREEN-VALLEY ELLIPTICAL GALAXY NGC 3226?

    Energy Technology Data Exchange (ETDEWEB)

    Appleton, P. N.; Bitsakis, T.; Alatalo, K. [NASAHerschel Science Center, Infrared Processing and Analysis Center, Caltech, 770S Wilson Avenue, Pasadena, CA 91125 (United States); Mundell, C. [Astrophysics Research Institute, John Moores University, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Lacy, M. [NRAO, Charlottesville, VA (United States); Armus, L. [Spitzer NASAHerschel Science Center, 1200 East California Boulevard, Caltech, Pasadena, CA 91125 (United States); Charmandaris, V. [Department of Physics, University of Crete, GR-71003 Heraklion (Greece); Duc, P.-A. [Service d' Astrophysique, Laboratoire AIM, CEA-Saclay, Orme des Merisiers, Bat 709, F-91191 Gif sur Yvette (France); Lisenfeld, U. [Dept. Fisica Teorica y del Cosmos, University of Granada, Edifica Mecenas, Granada (Spain); Ogle, P., E-mail: apple@ipac.caltech.edu [NASA Extragalactic Database, IPAC, Caltech, 1200 East California Boulevard, Caltech, Pasadena, CA 91125 (United States)

    2014-12-20

    We present archival Spitzer photometry and spectroscopy and Herschel photometry of the peculiar ''Green Valley'' elliptical galaxy NGC 3226. The galaxy, which contains a low-luminosity active galactic nucleus (AGN), forms a pair with NGC 3227 and is shown to lie in a complex web of stellar and H I filaments. Imaging at 8 and 16 μm reveals a curved plume structure 3 kpc in extent, embedded within the core of the galaxy and coincident with the termination of a 30 kpc long H I tail. In situ star formation associated with the infrared (IR) plume is identified from narrowband Hubble Space Telescope (HST) imaging. The end of the IR plume coincides with a warm molecular hydrogen disk and dusty ring containing 0.7-1.1 × 10{sup 7} M {sub ☉} detected within the central kiloparsec. Sensitive upper limits to the detection of cold molecular gas may indicate that a large fraction of the H{sub 2} is in a warm state. Photometry derived from the ultraviolet (UV) to the far-IR shows evidence for a low star-formation rate of ∼0.04 M {sub ☉} yr{sup –1} averaged over the last 100 Myr. A mid-IR component to the spectral energy distribution (SED) contributes ∼20% of the IR luminosity of the galaxy, and is consistent with emission associated with the AGN. The current measured star formation rate is insufficient to explain NGC 3226's global UV-optical ''green'' colors via the resurgence of star formation in a ''red and dead'' galaxy. This form of ''cold accretion'' from a tidal stream would appear to be an inefficient way to rejuvenate early-type galaxies and may actually inhibit star formation.

  14. The formation of Milky Way-mass disk galaxies in the first 500 million years of a cold dark matter universe

    CERN Document Server

    Feng, Yu; Croft, Rupert; Tenneti, Ananth; Bird, Simeon; Battaglia, Nicholas; Wilkins, Stephen

    2015-01-01

    In current cosmological models, galaxies form from the gravitational collapse of small perturbations in the matter distribution. This process involves both a hierarchy of merging structures and smooth accretion, so that early galaxies are predicted to be morphologically irregular, clumpy, and compact. This is supported by recent observational data on samples of galaxies at redshift $z=8$ and beyond. The volumes accessible to these studies, both computational and observational are however thousands of times smaller than those that will be probed by upcoming telescopes, such as WFIRST. As a result, studies so far have never been able to reach the realm of massive galaxies. Whether among the myriad tiny proto-galaxies there exists a population with similarities to present day galaxies is an open question. Here we show, using BlueTides, the first hydrodynamic simulation large enough to resolve the relevant scales, that the first massive galaxies to form are in fact predicted to have extensive rotationally-support...

  15. The dark matter halo shape of edge-on disk galaxies - III. Modelling the HI observations: results

    CERN Document Server

    O'Brien, J C; van der Kruit, P C

    2010-01-01

    This is the third paper in a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. For this purpose we need to analyse the observed XV diagrams in edge-on galaxies to accurately measure the radial HI surface density, the rotation curve and the HI velocity dispersion. We present the results of the modelling of HI observations of 8 HI-rich, late-type, edge-on galaxies. In all of these we find differential rotation. Most systems display HI velocity dispersions of 6.5 to 7.5 km s$^{-1}$ and all except one show radial structure. There is an increase in the mean HI velocity dispersion with maximum rotation velocity, at least up to 120 km s$^{-1}$. Next we analyse the observations to derive the radial variation of the thickness (flaring) of the HI layer. We find that with the exception of the asymmetric IC5052, all of the galaxies in our sample are good candidates for 3D mass modelling to measure the dark halo shape. The flaring profiles are symmetric and have a common shape...

  16. The Properties of Spiral Galaxies in Semi-Analytic Galaxy Formation Models

    OpenAIRE

    2000-01-01

    We examine the present-day galaxy disk colors and star formation rates (SFRs) in the semi-analytic model of Cole et al. (2000). We find that the fiducial model is a good match to Kennicutt's (1998) observed global star formation law, the color-based metallicity-magnitude correlation and the colors of low-luminosity galaxies. The main limitation of the model, from the point of view of present-day spirals, is that the optical colors of the disks of very luminous spiral galaxies are too blue, ev...

  17. VLT/X-shooter observations of blue compact galaxies Haro 11 and ESO 338-IG 004

    Science.gov (United States)

    Guseva, N. G.; Izotov, Y. I.; Fricke, K. J.; Henkel, C.

    2012-05-01

    Context. Strongly star-forming galaxies of subsolar metallicities are typical of the high-redshift universe. Here we therefore provide accurate data for two low-z analogs, the well-known low-metallicity emission-line galaxies Haro 11 and ESO 338-IG 004. Aims: Our main goal is to derive their spectroscopic properties and to examine whether a previously reported near-infrared (NIR) excess in Haro 11 can be confirmed. Methods: On the basis of Very Large Telescope/X-shooter spectroscopic observations in the wavelength range ~λλ3000-24 000 Å, we use standard direct methods to derive physical conditions and element abundances. Furthermore, we use X-shooter data together with Spitzer observations in the mid-infrared range to attempt to find hidden star formation. Results: We derive interstellar oxygen abundances of 12 + log O/H = 8.33 ± 0.01, 8.10 ± 0.04, and 7.89 ± 0.01 in the two H ii regions B and C of Haro 11 and in ESO 338-IG 004, respectively. The observed fluxes of the hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value of the extinction coefficient C(Hβ) across the entire wavelength range from the near-ultraviolet to the NIR and mid-infrared for each of the studied H ii regions. Thus, we confirm our previous findings obtained for several low-metallicity emission-line galaxies (Mrk 59, II Zw 40, Mrk 71, Mrk 996, SBS 0335-052E, PHL 293B, and GRB HG 031203) that the extinction coefficient C(Hβ) is not higher in the NIR than in the optical range and therefore that there are no emission-line regions contributing to the line emission in the NIR range, which are hidden in the optical range. The agreement between the extinction-corrected and CLOUDY-predicted fluxes implies that a H ii region model including only stellar photoionisation is able to account for the observed fluxes, in both the optical and NIR ranges. No additional excitation mechanism such as shocks from stellar winds and supernova

  18. Sloshing cold fronts in galaxy groups and their perturbing disk galaxies: an X-ray, Optical and Radio Case Study

    CERN Document Server

    Gastaldello, F; Ghizzardi, S; Giacintucci, S; Girardi, M; Roediger, E; Rossetti, M; Brighenti, F; Buote, D A; Eckert, D; Ettori, S; Humphrey, P J; Mathews, W G

    2013-01-01

    We present a combined X-ray, optical, and radio analysis of the galaxy group IC 1860 using the currently available Chandra and XMM data, literature multi-object spectroscopy data and GMRT data. The Chandra and XMM imaging and spectroscopy reveal two surface brightness discontinuities at 45 and 76 kpc shown to be consistent with a pair of cold fronts. These features are interpreted as due to sloshing of the central gas induced by an off-axis minor merger with a perturber. This scenario is further supported by the presence of a peculiar velocity of the central galaxy IC 1860 and the ide

  19. Variations in the Star Formation Efficiency of the Dense Molecular Gas across the Disks of Star-Forming Galaxies

    CERN Document Server

    Usero, Antonio; Walter, Fabian; Schruba, Andreas; García-Burillo, Santiago; Sandstrom, Karin; Bigiel, Frank; Brinks, Elias; Kramer, Carsten; Rosolowsky, Erik; Schuster, Karl-Friedrich; de Blok, W J G

    2015-01-01

    We present a new survey of HCN(1-0) emission, a tracer of dense molecular gas, focused on the little-explored regime of normal star-forming galaxy disks. Combining HCN, CO, and infrared (IR) emission, we investigate the role of dense gas in Star Formation (SF), finding systematic variations in both the apparent dense gas fraction and the apparent SF efficiency (SFE) of dense gas. The latter may be unexpected, given the popularity of gas density threshold models to explain SF scaling relations. We used the IRAM 30-m telescope to observe HCN(1-0) across 29 nearby disk galaxies whose CO(2-1) emission has previously been mapped by the HERACLES survey. Because our observations span a range of galactocentric radii, we are able to investigate the properties of the dense gas as a function of local conditions. We focus on how the IR/CO, HCN/CO, and IR/HCN ratios (observational cognates of the SFE, dense gas fraction, and dense gas SFE) depend on the stellar surface density and the molecular/atomic ratio. The HCN/CO ra...

  20. The nature of the red disk-like galaxies at high redshift: dust attenuation and intrinsically red stellar populations

    CERN Document Server

    Pierini, D; Gordon, K D; Witt, A N

    2005-01-01

    We investigate which conditions of dust attenuation and stellar populations allow models of dusty, continuously star-forming, bulge-less disk galaxies at 0.85.3, Ic-K>4, J-K>2.3). As a main novelty, we use stellar population models that include the thermally pulsating Asymptotic Giant Branch (TP-AGB) phase of stellar evolution. The star formation rate of the models declines exponentially as a function of time, the e-folding time being longer than 3 Gyr. In addition, we use calculations of radiative transfer of the stellar and scattered radiation through different dusty interstellar media in order to explore the wide parameter space of dust attenuation. We find that synthetic disks can exhibit red optical/near-infrared colours because of reddening by dust, but only if they have been forming stars for at least about 1 Gyr. Extremely few models barely exhibit Rc-K>5.3, if the inclination i=90 deg and if the opacity 2*tauV>6. Hence, Rc-K-selected galaxies at 10.5. This explains the large fraction of observed, edg...

  1. A Catalog of Bulge+Disk Decompositions and Updated Photometry for 1.12 Million Galaxies in the Sloan Digital Sky Survey

    CERN Document Server

    Simard, Luc; Patton, David R; Ellison, Sara L; McConnachie, Alan W

    2011-01-01

    We perform two-dimensional, Point-Spread-Function-convolved, bulge+disk decompositions in the $g$ and $r$ bandpasses on a sample of 1,123,718 galaxies from the Legacy area of the Sloan Digital Sky Survey Data Release Seven. Four different decomposition procedures are investigated which make improvements to sky background determinations and object deblending over the standard SDSS procedures that lead to more robust structural parameters and integrated galaxy magnitudes and colors, especially in crowded environments. We use a set of science-based quality assurance metrics namely the disk luminosity-size relation, the galaxy color-magnitude diagram and the galaxy central (fiber) colors to show the robustness of our structural parameters. The best procedure utilizes simultaneous, two-bandpass decompositions. Bulge and disk photometric errors remain below 0.1 mag down to bulge and disk magnitudes of $g \\simeq 19$ and $r \\simeq 18.5$. We also use and compare three different galaxy fitting models: a pure Sersic mod...

  2. The VIMOS Public Extragalactic Redshift Survey (VIPERS): Downsizing of the blue cloud and the influence of galaxy size on mass quenching over the last eight billion years

    CERN Document Server

    Haines, C P; Guzzo, L; Davidzon, I; Bolzonella, M; Garilli, B; Scodeggio, M; Granett, B R; de la Torre, S; De Lucia, G; Abbas, U; Adami, C; Arnouts, S; Bottini, D; Cappi, A; Cucciati, O; Franzetti, P; Fritz, A; Gargiulo, A; Brun, V Le; Fevre, O Le; Maccagni, D; Malek, K; Marulli, F; Moutard, T; Polletta, M; Pollo, A; Tasca, L A M; Tojeiro, R; Vergani, D; Zanichelli, A; Zamorani, G; Bel, J; Branchini, E; Coupon, J; Ilbert, O; Moscardini, L; Peacock, J A; Siudek, M

    2016-01-01

    We use the full VIPERS redshift survey in combination with SDSS-DR7 to explore the relationships between star-formation history (using d4000), stellar mass and galaxy structure, and how these relationships have evolved since z~1. We trace the extents and evolutions of both the blue cloud and red sequence, by fitting double Gaussians to the d4000 distribution of galaxies in narrow stellar mass bins, for four redshift intervals over 010^11Msun, d4000<1.55) drops sharply by a factor five between z~0.8 and z~0.5. These galaxies are becoming quiescent at a rate that largely matches the increase in the numbers of massive passive galaxies seen over this period. We examine the size-mass relation of blue cloud galaxies, finding that its high-mass boundary runs along lines of constant M*/r_e or equivalently inferred velocity dispersion. Larger galaxies can continue to form stars to higher stellar masses than smaller galaxies. As blue cloud galaxies approach this high-mass limit, they start to be quenched, their d400...

  3. E/S0 Galaxies on the Blue Color-Stellar Mass Sequence at z=0: Fading Mergers or Future Spirals?

    CERN Document Server

    Kannappan, S J; Baker, A J

    2009-01-01

    We identify a population of morphologically defined E/S0 galaxies lying on the blue sequence at the present epoch. Using three samples, we analyze blue-sequence E/S0s with stellar masses >10^8 Msun, arguing that individual objects may be evolving either up toward the red sequence or down into the blue sequence. Blue-sequence E/S0 galaxies become more common with decreasing stellar mass, comprising 5% near the "bimodality mass" M_b ~ 3 x 10^10 Msun, and sharply rising to >20-30% below the "threshold mass" M_t ~ 4-6 x 10^9 Msun. The strong emergence of blue-sequence E/S0s below M_t coincides with a previously reported global increase in mean atomic gas fractions below M_t for galaxies of all types on both sequences, suggesting that the availability of cold gas may be basic to blue-sequence E/S0s' existence. Environmental analysis reveals that many sub-M_b blue-sequence E/S0s reside in low to intermediate density environments. In mass-radius and mass-sigma scaling relations, blue-sequence E/S0s are more similar ...

  4. CONTRIBUTION OF THE ACCRETION DISK, HOT CORONA, AND OBSCURING TORUS TO THE LUMINOSITY OF SEYFERT GALAXIES: INTEGRAL AND SPITZER OBSERVATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Sazonov, S.; Churazov, E.; Krivonos, R.; Revnivtsev, M.; Sunyaev, R.; Vikhlinin, A. [Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, Moscow 117997 (Russian Federation); Willner, S. P.; Goulding, A. D.; Jones, C.; Murray, S. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Gorjian, V.; Werner, M. W. [Jet Propulsion Laboratory, California Institute of Technology, MS 169-327, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Forman, W. R. [Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild-Str. 1, D-85741 Garching (Germany)

    2012-10-01

    We estimate the relative contributions of the supermassive black hole (SMBH) accretion disk, corona, and obscuring torus to the bolometric luminosity of Seyfert galaxies, using Spitzer mid-infrared (MIR) observations of a complete sample of 68 nearby active galactic nuclei (AGNs) from the INTEGRAL all-sky hard X-ray (HX) survey. This is the first HX-selected (above 15 keV) sample of AGNs with complementary high angular resolution, high signal-to-noise, MIR data. Correcting for the host galaxy contribution, we find a correlation between HX and MIR luminosities: L{sub 15{mu}m}{proportional_to}L{sup 0.74{+-}0.06}{sub HX}. Assuming that the observed MIR emission is radiation from an accretion disk reprocessed in a surrounding dusty torus that subtends a solid angle decreasing with increasing luminosity (as inferred from the declining fraction of obscured AGNs), the intrinsic disk luminosity, L{sub Disk}, is approximately proportional to the luminosity of the corona in the 2-300 keV energy band, L{sub Corona}, with the L{sub Disk}/L{sub Corona} ratio varying by a factor of 2.1 around a mean value of 1.6. This ratio is a factor of {approx}2 smaller than for typical quasars producing the cosmic X-ray background. Therefore, over three orders of magnitude in luminosity, HX radiation carries a large, and roughly comparable, fraction of the bolometric output of AGNs. We estimate the cumulative bolometric luminosity density of local AGNs at {approx}(1-3) Multiplication-Sign 10{sup 40} erg s{sup -1} Mpc{sup -3}. Finally, the Compton temperature ranges between kT{sub c} Almost-Equal-To 2 and Almost-Equal-To 6 keV for nearby AGNs, compared to kT{sub c} Almost-Equal-To 2 keV for typical quasars, confirming that radiative heating of interstellar gas can play an important role in regulating SMBH growth.

  5. A Study in Blue: The Baryon Content of Isolated Low Mass Galaxies

    CERN Document Server

    Bradford, Jeremy D; Blanton, Michael R

    2015-01-01

    We study the baryon content of low mass galaxies selected from the Sloan Digital Sky Survey (SDSS DR8), focusing on galaxies in isolated environments where the complicating physics of galaxy-galaxy interactions are minimized. We measure neutral hydrogen (HI) gas masses and line-widths for 148 isolated galaxies with stellar mass between $10^7$ and $10^{9.5} M_{\\odot}$. We compare isolated low mass galaxies to more massive galaxies and galaxies in denser environments by remeasuring HI emission lines from the Arecibo Legacy Fast ALFA (ALFALFA) survey 40% data release. All isolated low mass galaxies either have large atomic gas fractions or large atomic gas fractions cannot be ruled out via their upper limits. We measure a median atomic gas fraction of $f_{\\rm gas} = 0.82 \\pm 0.13$ for our isolated low mass sample with no systems below 0.30. At all stellar masses, the correlations between galaxy radius, baryonic mass and velocity width are not significantly affected by environment. Finally, we estimate a median b...

  6. Inside Out and Upside Down: Tracing the Assembly of a Simulated Disk Galaxy Using Mono-Age Stellar Populations

    CERN Document Server

    Bird, Jonathan C; Weinberg, David H; Guedes, Javiera; Callegari, Simone; Mayer, Lucio; Madau, Piero

    2013-01-01

    We analyze the present-day structure and assembly history of a high resolution hydrodynamic simulation of the formation of a Milky Way (MW)-like disk galaxy, from the "Eris" simulation suite, dissecting it into cohorts of stars formed at different epochs of cosmic history. At z=0, stars with t_form 3 are quickly scattered into rounded, kinematically hot configurations. The oldest disk cohorts form in structures that are radially compact and relatively thick, while subsequent cohorts form in progressively larger, thinner, colder configurations from gas with increasing levels of rotational support. The disk thus forms "inside-out" in a radial sense and "upside-down" in a vertical sense. Secular heating and radial migration influence the final state of each age cohort, but the changes they produce are small compared to the trends established at formation. The predicted correlations of stellar age with spatial and kinematic structure are in good qualitative agreement with the correlations observed for mono-abunda...

  7. Galactic Disk Warps

    CERN Document Server

    Kuijken, K; Kuijken, Konrad; Garcia, Inigo

    2000-01-01

    This review addresses recent developments in the field of disk galaxy warps. Both results from a new HI survey of edgeon disk galaxies, and of simulations of the interaction between a disk+halo and an orbiting satelite, will be discussed.

  8. Galactic Disk Warps

    NARCIS (Netherlands)

    Kuijken, K.; García, I.

    2000-01-01

    Abstract: This review addresses recent developments in the field of disk galaxy warps. Both results from a new HI survey of edgeon disk galaxies, and of simulations of the interaction between a disk+halo and an orbiting satelite, will be discussed.

  9. The Stellar Masses of Disk Galaxies and the Calibration of Color-Mass to Light Ratio Relations

    CERN Document Server

    McGaugh, Stacy

    2013-01-01

    We present new Spitzer 3.6 micron observations of a sample of disk galaxies spanning over 10 magnitudes in luminosity and ranging in gas fraction from ~10% to over 90%. We use these data to test population synthesis prescriptions for computing stellar mass. Many commonly employed models fail to provide self-consistent stellar masses in the sense that the stellar mass estimated from the optical luminosity typically exceeds that estimated from the near-infrared (NIR) luminosity. This problem is present in models both with and without TP-AGB stars, but is more severe in the former. Self-consistency can be achieved if NIR mass-to-light ratios are approximately constant with a mean value near 0.5 Msun/Lsun at 3.6 microns. We use the Baryonic Tully-Fisher relation calibrated by gas rich galaxies to provide an independent estimate of the color-mass to light ratio relation. This approach also suggests that the typical 3.6 micron mass-to-light ratio is 0.5 (0.65 in the K band) for rotationally supported galaxies. Thes...

  10. The dark matter halo shape of edge-on disk galaxies - II. Modelling the HI observations: methods

    CERN Document Server

    O'Brien, J C; van der Kruit, P C

    2010-01-01

    This is the second paper of a series in which we attempt to put constraints on the flattening of dark halos in disk galaxies. For this purpose, we observe the HI in edge-on galaxies, where it is in principle possible to measure the force field in the halo vertically and radially from gas layer flaring and rotation curve decomposition respectively. To calculate the force fields, we need to analyse the observed XV diagrams to accurately measure all three functions that describe the planar kinematics and distribution of a galaxy: the radial HI surface density, the rotation curve and the HI velocity dispersion. In this paper, we discuss the improvements and limitations of the methods previously used to measure these HI properties. We extend the constant velocity dispersion method to include determination of the HI velocity dispersion as a function of galactocentric radius and perform extensive tests on the quality of the fits. We will apply this 'radial decomposition XV modelling method' to our HI observations of...

  11. Accretion-Inhibited Star Formation in the Warm Molecular Disk of the Green-valley Elliptical Galaxy NGC 3226

    CERN Document Server

    Appleton, P N; Bitsakis, T; Lacy, M; Alatalo, K; Armus, L; Charmandaris, V; Duc, P -A; Lisenfeld, U; Ogle, P

    2014-01-01

    We present archival Spitzer photometry and spectroscopy, and Herschel photometry, of the peculiar "Green Valley" elliptical galaxy NGC~3226. The galaxy, which contains a low-luminosity AGN, forms a pair with NGC~3227, and is shown to lie in a complex web of stellar and HI filaments. Imaging at 8 and 16$\\mu$m reveals a curved plume structure 3 kpc in extent, embedded within the core of the galaxy, and coincident with the termination of a 30 kpc-long HI tail. In-situ star formation associated with the IR plume is identified from narrow-band HST imaging. The end of the IR-plume coincides with a warm molecular hydrogen disk and dusty ring, containing 0.7-1.1 $\\times$ 10$^7$ M$_{\\odot}$ detected within the central kpc. Sensitive upper limits to the detection of cold molecular gas may indicate that a large fraction of the H$_2$ is in a warm state. Photometry, derived from the UV to the far-IR, shows evidence for a low star formation rate of $\\sim$0.04 M$_{\\odot}$ yr$^{-1}$ averaged over the last 100 Myrs. A mid-IR ...

  12. The evolution of the galaxy luminosity function in the rest frame blue band up to z=3.5

    CERN Document Server

    Poli, F; Fontana, A; Menci, N; Zamorani, G; Nonino, M; Saracco, P; Vanzella, E; Donnarumma, I; Salimbeni, S; Cimatti, A; Cristiani, S; Daddi, E; D'Odorico, S; Mignoli, M; Pozzetti, L; Renzini, A

    2003-01-01

    We present an estimate of the cosmological evolution of the field galaxy luminosity function (LF) in the rest frame 4400 Angstrom B -band up to redshift z=3.5. To this purpose, we use a composite sample of 1541 I--selected galaxies selected down to I_(AB)=27.2 and 138 galaxies selected down to K_(AB)=25 from ground-based and HST multicolor surveys, most notably the new deep JHK images in the Hubble Deep Field South (HDF-S) taken with the ISAAC instrument at the ESO-VLT telescope. About 21% of the sample has spectroscopic redshifts, and the remaining fraction well calibrated photometric redshifts. The resulting blue LF shows little density evolution at the faint end with respect to the local values, while at the bright end (M_B(AB)<-20) a brightening increasing with redshift is apparent with respect to the local LF. Hierarchical CDM models overpredict the number of faint galaxies by about a factor 3 at z=1. At the bright end the predicted LFs are in reasonable agreement only at low and intermediate redshift...

  13. The Properties of the Circumgalactic Medium in Red and Blue Galaxies: Results from the COS-GASS+COS-Halos Surveys

    CERN Document Server

    Borthakur, Sanchayeeta; Tumlinson, Jason; Bordoloi, Rongmon; Kauffmann, Guinevere; Catinella, Barbara; Schiminovich, David; Dave, Romeel; Moran, Sean M; Saintonge, Amelie

    2016-01-01

    We use the combined data from the COS-GASS and COS-Halos surveys to characterize the Circum-Galactic Medium (CGM) surrounding typical low-redshift galaxies in the mass range $\\rm~M_*\\sim~10^{9.5-11.5}~M_{\\odot} $, and over a range of impact parameters extending to just beyond the halo virial radius ($\\rm~R_{vir}$). We find the radial scale length of the distributions of the equivalent widths of the Lyman~$\\alpha$ and Si III absorbers to be 0.9 and 0.4 $\\rm~R_{vir}$, respectively. The radial distribution of equivalent widths is relatively uniform for the blue galaxies, but highly patchy (low covering fraction) for the red galaxies. We also find that the Lyman~$\\alpha$ and Si III equivalent widths show significant positive correlations with the specific star-formation rate (sSFR) of the galaxy. We find a surprising lack of correlations between the halo mass (virial velocity) and either the velocity dispersions or velocity offsets of the Lyman~$\\alpha$ lines. The ratio of the velocity offset to the velocity disp...

  14. SLOSHING COLD FRONTS IN GALAXY GROUPS AND THEIR PERTURBING DISK GALAXIES: AN X-RAY, OPTICAL, AND RADIO CASE STUDY

    Energy Technology Data Exchange (ETDEWEB)

    Gastaldello, Fabio; Di Gesu, Laura; Ghizzardi, Simona; Rossetti, Mariachiara [IASF-Milano, INAF, via Bassini 15, I-20133 Milan (Italy); Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Girardi, Marisa [Dipartimento di Fisica, Universita degli Studi di Trieste, Sezione di Astronomia, via Tiepolo 11, I-34133 Trieste (Italy); Roediger, Elke [Jacobs University Bremen, P.O. Box 750 561, D-28725 Bremen (Germany); Brighenti, Fabrizio [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Buote, David A.; Humphrey, Philip J. [Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575 (United States); Eckert, Dominique [ISDC Data Centre for Astrophysics, Geneva Observatory, ch. d' Ecogia, 16, CH-1290 Versoix (Switzerland); Ettori, Stefano [INAF, Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Mathews, William G. [UCO/Lick Observatory, University of California at Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-06-10

    We present a combined X-ray, optical, and radio analysis of the galaxy group IC 1860 using the currently available Chandra and XMM data, multi-object spectroscopy data from the literature, and Giant Metrewave Radio Telescope (GMRT) data. The Chandra and XMM imaging and spectroscopy reveal two surface brightness discontinuities at 45 and 76 kpc shown to be consistent with a pair of cold fronts. These features are interpreted as due to sloshing of the central gas induced by an off-axis minor merger with a perturber. This scenario is further supported by the presence of a peculiar velocity of the central galaxy IC 1860 and the identification of a possible perturber in the optically disturbed spiral galaxy IC 1859. The identification of the perturber is consistent with the comparison with numerical simulations of sloshing. The GMRT observation at 325 MHz shows faint, extended radio emission contained within the inner cold front, as seen in some galaxy clusters hosting diffuse radio mini-halos. However, unlike mini-halos, no particle reacceleration is needed to explain the extended radio emission, which is consistent with aged radio plasma redistributed by the sloshing. There is a strong analogy between the X-ray and optical phenomenology of the IC 1860 group and that of two other groups, NGC 5044 and NGC 5846, showing cold fronts. The evidence presented in this paper is among the strongest supporting the currently favored model of cold-front formation in relaxed objects and establishes the group scale as a chief environment for studying this phenomenon.

  15. Galaxy Zoo: Passive Red Spirals

    CERN Document Server

    Masters, Karen L; Romer, A Kathy; Nichol, Robert C; Bamford, Steven P; Schawinski, Kevin; Lintott, Chris J; Andreescu, Dan; Campbell, Heather C; Crowcroft, Ben; Doyle, Isabelle; Edmondson, Edward M; Murray, Phil; Raddick, M Jordan; Slosar, Anze; Szalay, Alexander S; Vandenberg, Jan

    2009-01-01

    We study the spectroscopic properties and environments of red spiral galaxies found by the Galaxy Zoo project. By carefully selecting face-on, disk dominated spirals we construct a sample of truly passive disks (not dust reddened, nor dominated by old stellar populations in a bulge). As such, our red spirals represent an interesting set of possible transition objects between normal blue spirals and red early types. We use SDSS data to investigate the physical processes which could have turned these objects red without disturbing their morphology. Red spirals prefer intermediate density regimes, however there are no obvious correlations between red spiral properties and environment - environment alone is not sufficient to determine if a galaxy will become a red spiral. Red spirals are a small fraction of spirals at low masses, but dominate at large stellar masses - massive galaxies are red independent of morphology. We confirm that red spirals have older stellar populations and less recent star formation than ...

  16. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. I. The flocculent galaxy M33

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2012-01-01

    We analyze the relationship between maximum cluster mass, M_max, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H2) and star formation rate (Sigma_SFR) in the flocculent galaxy M33, using published gas data and a catalog of more than 600 young star clusters in its disk. By comparing the radial distributions of gas and most massive cluster masses, we find that M_max is proportional to Sigma_gas^4.7, M_max is proportional Sigma_H2^1.3, and M_max is proportional to Sigma_SFR^1.0. We rule out that these correlations result from the size of sample; hence, the change of the maximum cluster mass must be due to physical causes.

  17. INSIDE OUT AND UPSIDE DOWN: TRACING THE ASSEMBLY OF A SIMULATED DISK GALAXY USING MONO-AGE STELLAR POPULATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Bird, Jonathan C.; Kazantzidis, Stelios; Weinberg, David H. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Guedes, Javiera [Institute for Astronomy, ETH Zuerich, Wolgang-Pauli-Strasse 27, CH-8093 Zuerich (Switzerland); Callegari, Simone [Anthropology Institute and Museum, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Mayer, Lucio [Institute for Theoretical Physics, University of Zuerich, Winterthurerstrasse 190, CH-8057 Zuerich (Switzerland); Madau, Piero [Department of Astronomy and Astrophysics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-08-10

    We analyze the present day structure and assembly history of a high-resolution hydrodynamic simulation of the formation of a Milky-Way-(MW)-like disk galaxy, from the ''Eris'' simulation suite, dissecting it into cohorts of stars formed at different epochs of cosmic history. At z = 0, stars with t{sub form} < 2 Gyr mainly occupy the stellar spheroid, with the oldest (earliest forming) stars having more centrally concentrated profiles. The younger age cohorts populate disks of progressively longer radial scale lengths and shorter vertical scale heights. At a given radius, the vertical density profiles and velocity dispersions of stars vary smoothly as a function of age, and the superposition of old, vertically extended and young, vertically compact cohorts gives rise to a double-exponential profile like that observed in the MW. Turning to formation history, we find that the trends of spatial structure and kinematics with stellar age are largely imprinted at birth, or immediately thereafter. Stars that form during the active merger phase at z > 3 are quickly scattered into rounded, kinematically hot configurations. The oldest disk cohorts form in structures that are radially compact and relatively thick, while subsequent cohorts form in progressively larger, thinner, colder configurations from gas with increasing levels of rotational support. The disk thus forms ''inside out'' in a radial sense and ''upside down'' in a vertical sense. Secular heating and radial migration influence the final state of each age cohort, but the changes they produce are small compared to the trends established at formation. The predicted correlations of stellar age with spatial and kinematic structure are in good qualitative agreement with the correlations observed for mono-abundance stellar populations in the MW.

  18. PLAYING WITH POSITIVE FEEDBACK: EXTERNAL PRESSURE-TRIGGERING OF A STAR-FORMING DISK GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Bieri, Rebekka; Dubois, Yohan; Silk, Joseph; Mamon, Gary A., E-mail: bieri@iap.fr [Institut d’Astrophysique de Paris (UMR 7095: CNRS and UPMC—Sorbonne Universités), 98 bis bd Arago, F-75014 Paris (France)

    2015-10-20

    In massive galaxies, the currently favored method for quenching star formation is via active galactic nuclei (AGN) feedback, which ejects gas from the galaxy using a central supermassive black hole. At high redshifts however, explanation of the huge rates of star formation often found in galaxies containing AGNs may require a more vigorous mode of star formation than is attainable by simply enriching the gas content of galaxies in the usual gravitationally driven mode that is associated with the nearby universe. Using idealized hydrodynamical simulations, we show that AGN-pressure-driven star formation potentially provides the positive feedback that may be required to generate the accelerated star formation rates observed in the distant universe.

  19. The SWELLS survey. II. Breaking the disk-halo degeneracy in the spiral galaxy gravitational lens SDSS J2141-0001

    CERN Document Server

    Dutton, A A; Marshall, P J; Auger, M W; Treu, T; Koo, D C; Bolton, A S; Holden, B P; Koopmans, L V E

    2011-01-01

    The degeneracy among the disk, bulge and halo contributions to galaxy rotation curves prevents an understanding of the distribution of baryons and dark matter in disk galaxies. In an attempt to break this degeneracy, we present an analysis of the spiral galaxy strong gravitational lens SDSS J2141-0001, discovered as part of the SLACS survey. We present new Hubble Space Telescope multicolor imaging, gas and stellar kinematics data derived from long-slit spectroscopy, and K-band LGS adaptive optics imaging, both from the Keck telescopes. We model the galaxy as a sum of concentric axisymmetric bulge, disk and halo components and infer the contribution of each component, using information from gravitational lensing and gas kinematics. This analysis yields a best-fitting total (disk plus bulge) stellar mass of log_{10}(Mstar/Msun)=10.99(+0.11,-0.25). The photometric data combined with stellar population synthesis models yield log_{10}(Mstar/Msun)=10.97\\pm0.07, and 11.21\\pm0.07 for the Chabrier and Salpeter IMFs, r...

  20. Removing Biases in Resolved Stellar Mass Maps of Galaxy Disks through Successive Bayesian Marginalization

    Science.gov (United States)

    Martínez-García, Eric E.; González-Lópezlira, Rosa A.; Magris C., Gladis; Bruzual A., Gustavo

    2017-01-01

    Stellar masses of galaxies are frequently obtained by fitting stellar population synthesis models to galaxy photometry or spectra. The state of the art method resolves spatial structures within a galaxy to assess the total stellar mass content. In comparison to unresolved studies, resolved methods yield, on average, higher fractions of stellar mass for galaxies. In this work we improve the current method in order to mitigate a bias related to the resolved spatial distribution derived for the mass. The bias consists in an apparent filamentary mass distribution and a spatial coincidence between mass structures and dust lanes near spiral arms. The improved method is based on iterative Bayesian marginalization, through a new algorithm we have named Bayesian Successive Priors (BSP). We have applied BSP to M51 and to a pilot sample of 90 spiral galaxies from the Ohio State University Bright Spiral Galaxy Survey. By quantitatively comparing both methods, we find that the average fraction of stellar mass missed by unresolved studies is only half what previously thought. In contrast with the previous method, the output BSP mass maps bear a better resemblance to near-infrared images.

  1. Multiple minor mergers: formation of elliptical galaxies and constraints for the growth of spiral disks

    CERN Document Server

    Bournaud, Frederic; Combes, Francoise

    2007-01-01

    Multiple, sequential mergers are unavoidable in the hierarchical build-up picture of galaxies, in particular for the minor mergers that are frequent and highly likely to have occured several times for most present-day galaxies. However the effect of repeated minor mergers on galactic structure and evolution has not been studied systematically so far. In this paper, we present a numerical study of multiple, subsequent, minor galaxy mergers, with various mass ratios ranging from 4:1 to 50:1. The N-body simulations include gas dynamics and star formation. We study the morphological and kinematical properties of the remnants, and show that several so-called "minor" mergers can lead to the formation of elliptical-like galaxies, that have global morphological and kinematical properties similar to that observed in real elliptical galaxies. The properties of these systems are compared with that of elliptical galaxies produced by the standard scenario of one single major merger. We thus show that repeated minor merger...

  2. Gas surface density, star formation rate surface density, and the maximum mass of young star clusters in a disk galaxy. II. The grand-design galaxy M51

    CERN Document Server

    Gonzalez-Lopezlira, Rosa A; Kroupa, Pavel

    2013-01-01

    We analyze the relationship between maximum cluster mass, and surface densities of total gas (Sigma_gas), molecular gas (Sigma_H_2), neutral gas (Sigma_HI) and star formation rate (Sigma_SFR) in the grand design galaxy M51, using published gas data and a catalog of masses, ages, and reddenings of more than 1800 star clusters in its disk, of which 223 are above the cluster mass distribution function completeness limit. We find for clusters older than 25 Myr that M_3rd, the median of the 5 most massive clusters, is proportional to Sigma_HI^0.4. There is no correlation with Sigma_gas, Sigma_H2, or Sigma_SFR. For clusters younger than 10 Myr, M_3rd is proportional to Sigma_HI^0.6, M_3rd is proportional to Sigma_gas^0.5; there is no correlation with either Sigma_H_2 or Sigma_SFR. The results could hardly be more different than those found for clusters younger than 25 Myr in M33. For the flocculent galaxy M33, there is no correlation between maximum cluster mass and neutral gas, but M_3rd is proportional to Sigma_g...

  3. The Structure and Stellar Content of the Outer Disks of Galaxies: A New View from the Pan-STARRS1 Medium Deep Survey

    CERN Document Server

    Zheng, Z; Heckman, T; Meurer, G; Burgett, W; Chambers, K; Huber, M; Kaiser, N; Magnier, E; Metcalfe, N; Price, P; Tonry, J; Wainscoat, R; Waters, C

    2014-01-01

    We present the results of an analysis of Pan-STARRS1 Medium Deep Survey multi-band (g,r,i,z,y) images of a sample of 698 low-redshift disk galaxies that span broad ranges in stellar mass, star-formation rate, and bulge/disk ratio. We use population synthesis SED fitting techniques to explore the radial distribution of the light, color, surface mass density, mass/light ratio, and age of the stellar populations. We characterize the structure and stellar content of the galaxy disks out to radii of about twice Petrosian r90, beyond which the halo light becomes significant. We measure normalized radial profiles for sub-samples of galaxies in three bins each of stellar mass and concentration. We also fit radial profiles to each galaxy. The majority of galaxies have down-bending radial surface brightness profiles in the bluer bands with a break radius at roughly r90. However, they typically show single unbroken exponentials in the reddest bands and in the stellar surface mass density. We find that the mass/light rat...

  4. Herschel's "Cold Debris Disks": Background Galaxies or Quiescent Rims of Planetary Systems?

    CERN Document Server

    Krivov, A V; Löhne, T; Marshall, J P; Montesinos, B; del Burgo, C; Absil, O; Ardila, D; Augereau, J -C; Bayo, A; Bryden, G; Danchi, W; Ertel, S; Lebreton, J; Liseau, R; Mora, A; Mustill, A J; Mutschke, H; Neuhäuser, R; Pilbratt, G L; Roberge, A; Schmidt, T O B; Stapelfeldt, K R; Thébault, Ph; Vitense, Ch; White, G J; Wolf, S

    2013-01-01

    (abridged) Infrared excesses associated with debris disk host stars detected so far peak at wavelengths around ~100{\\mu}m or shorter. However, six out of 31 excess sources in the Herschel OTKP DUNES have been seen to show significant - and in some cases extended - excess emission at 160{\\mu}m, which is larger than the 100{\\mu}m excess. This excess emission has been suggested to stem from debris disks colder than those known previously. Using several methods, we re-consider whether some or even all of the candidates may be associated with unrelated galactic or extragalactic emission and conclude that it is highly unlikely that none of the candidates represents a true circumstellar disk. For true disks, both the dust temperatures inferred from the SEDs and the disk radii estimated from the images suggest that the dust is nearly as cold as a blackbody. This requires the grains to be larger than ~100{\\mu}m, regardless of their material composition. To explain the dearth of small grains, we explore several conceiv...

  5. Gravitational Instabilities in Two-Component Galaxy Disks with Gas Dissipation

    CERN Document Server

    Elmegreen, Bruce G

    2011-01-01

    Growth rates for gravitational instabilities in a thick disk of gas and stars are determined for a turbulent gas that dissipates on the local crossing time. The scale heights are derived from vertical equilibrium. The accuracy of the usual thickness correction, 1/(1+kH), is better than 6% in the growth rate when compared to exact integrations for the gravitational acceleration in the disk. Gas dissipation extends the instability to small scales, removing the minimum Jeans length. This makes infinitesimally thin disks unstable for all Toomre-Q values, and reasonably thick disks stable at high Q primarily because of thickness effects. The conventional gas+star threshold, Qtot increases from ~1 without dissipation to 2 or 3 when dissipation has a rate equal to the crossing rate over a perturbation scale. Observations of Qtot~2-3 and the presence of supersonic turbulence suggest that disks are unstable over a wide range of scales. Such instabilities drive spiral structure if there is shear and clumpy structure if...

  6. Optical and Near Infrared studies of the photometric structure and starburst activity of Blue Compact Dwarf Galaxies

    Science.gov (United States)

    Noeske, K. G.

    2003-03-01

    This thesis describes three studies of Blue Compact Dwarf Galaxies (BCDs), focussed on the structure of the stellar components, the star-forming activity, and the environment of such galaxies, as well as the physical background of their morphological variety. The analysis of deep Near Infrared (NIR) image data of a significant sample of BCDs allows to study the evolved stellar low surface brightness (LSB) components of BCDs more precisely than previous studies at visible wavelengths. Azimuthally averaged radial surface brightness profiles (SBPs) show an exponential intensity distribution of the stellar LSB components at large galactocentric radii. This result, along with the derived exponential scale lengths which are systematically smaller than those of dwarf Irregular and dwarf Elliptical galaxies, agrees with previous optical studies. Towards smaller radii, however, the NIR data reveal an inwards-flattening of the SBPs of the stellar LSB components with respect to their outer exponential slopes in more than half of the BCDs under study. Such inwards-flattening exponential SBPs are frequent in dwarf Irregulars and dwarf Ellipticals, but were hitherto largely undiscovered in the stellar hosts of BCDs. The physical origin of such SBPs in dwarf galaxies is to date not understood. Empirical approaches to their systematization and quantitative investigation are discussed, along with the various implications of the discovery of such SBPs in many BCDs for the understanding of such galaxies. Based on the derived structural information on the stellar LSB components and the starburst components, the hypothesis is raised that below a certain threshold density of the stellar LSB component, of the order of 0.4 solar masses per cubic parsec, burst-like star formation does not occur in gas-rich dwarf galaxies. On this hypothesis, the observed relations between the structure of the stellar LSB components of BCDs and their luminosity can be reproduced, as well as the systematic

  7. The role of major gas-rich mergers on the evolution of galaxies from the blue cloud to the red sequence

    CERN Document Server

    Guo, Rui; Xia, X Y; Mao, Shude; Shi, Yong

    2016-01-01

    With the aim of exploring the fast evolutionary path from the blue cloud of star-forming galaxies to the red sequence of quiescent galaxies in the local universe, we select a local advanced merging infrared luminous and ultraluminous galaxy (adv-merger (U)LIRGs) sample and perform careful dust extinction corrections to investigate their positions in the SFR-$M_{\\ast}$, u-r and NUV-r color-mass diagrams. The sample consists of 89 (U)LIRGs at the late merger stage, obtained from cross-correlating the IRAS Point Source Catalog Redshift Survey and 1 Jy ULIRGs samples with the Sloan Digital Sky Survey DR7 database. Our results show that $74\\%\\pm 5\\%$ of adv-merger (U)LIRGs are localized above the $1\\, \\sigma$ line of the local star-forming galaxy main sequence. We also find that all adv-merger (U)LIRGs are more massive than and as blue as the blue cloud galaxies after corrections of Galactic and internal dust extinctions, with $95\\%\\pm 2\\%$ and $81\\%\\pm 4\\%$ of them outside the blue cloud on the u-r and NUV-r colo...

  8. A Connection Between Bulge Properties and the Bimodality of Galaxies

    CERN Document Server

    Drory, Niv

    2007-01-01

    The global colors of galaxies have recently been shown to follow bimodal distributions. Galaxies separate into a ``red sequence'', populated prototypically by early-type galaxies, and a ``blue cloud'', whose typical objects are late-type disk galaxies. Intermediate-type (Sa-Sbc) galaxies populate both regions. It has been suggested that this bimodality reflects the two-component nature of disk-bulge galaxies. However, it has now been established that there are two types of bulges: ``classical bulges'' that are dynamically hot systems resembling (little) ellipticals, and ``pseudobulges'', dynamically cold, flattened, disk-like structures that could not have formed via violent relaxation. Therefore thee question is whether at types Sa-Sbc, where both bulge types are found, the red-blue dichotomy separates galaxies at some value of disk-to-bulge ratio, $B/T$, or, whether it separates galaxies of different bulge type, irrespective of their $B/T$. We identify classical bulges and pseudobulges morphologically with ...

  9. Properties of free-free, dust, and CO emissions in the starbursts of blue compact dwarf galaxies

    CERN Document Server

    Hirashita, Hiroyuki

    2012-01-01

    The central star-forming regions in three blue compact dwarf galaxies (He 2-10, NGC 5253, and II Zw 40) were observed in the 340 GHz (880 micron) band at 5 arcsec resolution with the Submillimetre Array (SMA). Continuum emission associated with the central star-forming complex was detected in all these galaxies. The SMA 880 micron flux is decomposed into free-free emission and dust emission by using centimetre-wavelength data in the literature. We find that free-free emission contributes half or more of the SMA 880 micron flux in the central starbursts in those three galaxies. In spite of the dominance of free-free emission at 880 micron, the radio-to-far infrared (FIR) ratios in the central star-forming regions are not significantly higher than those of the entire systems, showing the robustness of radio-FIR relation. Based on the robustness of the radio-FIR relation, we argue that the free--free fraction in the 880 micron emission is regulated by the dust temperature. We also analyze the CO (J = 3--2) emiss...

  10. Dissecting the Assembly Histories of Spheroidal Post-merger and Unusually Blue Elliptical Galaxies from the SDSS

    Science.gov (United States)

    McIntosh, Daniel H.; Haines, Tim; Sanchez, Sebastian; Tremonti, Christina A.; Rudnick, Gregory

    2015-01-01

    The modern merger hypothesis predicts the formation of new elliptical galaxies (Es) through the merging of two equal-mass, gas-rich spirals. Under the right conditions, simulations predict that such mergers produce a strong, central burst of star formation (SF) in the remnant. If merger-induced SF is subsequently quenched, this scenario offers an attractive blue-to-red migration channel to explain the buildup of massive quiescent galaxies over cosmic time. To test this prediction, we study 12 high-mass (Mstar>1e10 Msun), nearby (z1 R50, dust-reddened core colors, and inner morphological features (rings, dust). These galaxies are the best candidates for a "frosting" of young stars a top an older population, and their properties are consistent with a recent accretion of a gas-rich satellite. The remaining 5 Es are inconsistent with the merger hypothesis. They have quiescent-like indices, strong radial index gradients suggesting older core stars, and 80% exhibit broad LSB asymmetries at large radii that are consistent with being remnants of recent gas-poor (dry) merging.

  11. A VLT VIMOS integral field spectroscopic study of perturbed blue compact galaxies: UM 420 and UM 462

    CERN Document Server

    James, B L; Barlow, M J

    2009-01-01

    We report on optical integral field spectroscopy of two unrelated blue compact galaxies mapped with the 13 x 13 arcsec^2 VIMOS integral field unit at a resolution of 0.33 x 0.33 arcsec^2. Continuum and background subtracted emission line maps in the light of [O III] 5007, H-alpha, and [N II] 6584 are presented. Both galaxies display signs of ongoing perturbation and/or interaction. UM 420 is resolved for the first time to be a merging system composed of two starbursting components with an 'arm-like' structure associated with the largest component. UM 462 which is a disrupted system of irregular morphology is resolved into at least four starbursting regions. Maps of the H-alpha radial velocity and FWHM are discussed. No underlying broad line region was detected from either galaxy as the emission lines are well-fitted with single Gaussian profiles only. Electron temperatures and densities as well as the abundances of helium, oxygen, nitrogen, and sulphur were computed from spectra integrated over the whole gala...

  12. NGC 5044-N50: a link between blue compact galaxies and dwarf ellipticals

    Science.gov (United States)

    Cellone, Sergio A.; Buzzoni, Alberto

    We present new optical observations of the dwarf galaxy N50 in the NGC 5044 Group, showing that this object is probably at an intermediate BCD→dE evolutionary stage, after a realtively recent burst of star formation.

  13. Dynamical stability and environmental influences in low surface brightness disk galaxies

    NARCIS (Netherlands)

    Mihos, C.; McGaugh, S. S.; Blok, E. de

    1997-01-01

    Using analytic stability criteria we demonstrate that, because of their low surface mass density and large dark matter content, low surface brightness (LSB) disks are quite stable against the growth of global nonaxisymmetric modes such as bars. However, depending on their (poorly constrained) stella

  14. Unified Rotation Curve of the Galaxy -- Decomposition into de Vaucouleurs Bulge, Disk, Dark Halo, and the 9-kpc Rotation Dip --

    CERN Document Server

    Sofue, Y; Omodaka, T

    2008-01-01

    We present a unified rotation curve of the Galaxy re-constructed from the existing data by re-calculating the distances and velocities for a set of galactic constants R_0=8 kpc and V_0=200 km/s. We decompose it into a bulge with de Vaucouleurs-law profile of half-mass scale radius 0.5 kpc and mass 1.8 x 10^{10}M_{sun}, an exponential disk of scale radius 3.5 kpc of 6.5 x 10^{10}M_{sun}, and an isothermal dark halo of terminal velocity 200 km/s. The r^{1/4}-law fit was obtained for the first time for the Milky Way's rotation curve. After fitting by these fundamental structures, two local minima, or the dips, of rotation velocity are prominent at radii 3 and 9 kpc. The 3-kpc dip is consistent with the observed bar. It is alternatively explained by a massive ring with the density maximum at radius 4 kpc. The 9-kpc dip is clearly exhibited as the most peculiar feature in the galactic rotation curve. We explain it by a massive ring of amplitude as large as 0.3 to 0.4 times the disk density with the density peak at...

  15. Ultra-High-Density Molecular Core and Warped Nuclear Disk in the Deep Potential of Radio Lobe Galaxy NGC 3079

    Science.gov (United States)

    Sofue, Y.; Koda, J.; Kohno, K.; Okumura, S. K.; Honma, M.; Kawamura, A.; Irwin, Judith A.

    2001-02-01

    We have performed high-resolution synthesis observations of the 12CO (J=1-0) line emission from the radio lobe edge-on spiral galaxy NGC 3079 using a seven-element millimeter-wave interferometer at the Nobeyama Radio Observatory, which consisted of the 45 m telescope and six-element array. The nuclear molecular disk (NMD) of 750 pc radius is found to be inclined by 20° from the optical disk, and the NMD has spiral arms. An ultra-high-density core (UHC) of molecular gas was found at the nucleus. The gaseous mass of the UHC within 125 pc radius is as large as ~3×108 Msolar, an order of magnitude more massive than that in the same area of the Galactic center, and the mean density is as high as ~3×103H2 cm-3. A position-velocity diagram along the major axis indicates that the rotation curve already starts at a finite velocity exceeding 300 km s-1 from the nucleus. The surface mass density in the central region is estimated to be as high as ~105 Msolar pc-2, producing a very deep gravitational potential. We argue that the very large differential rotation in such a deep potential will keep the UHC gravitationally stable during the current star formation.

  16. VIMOS mosaic integral-field spectroscopy of the bulge and disk of the early-type galaxy NGC 4697

    CERN Document Server

    Spiniello, C; Coccato, L; Pota, V; Romanowsky, A J; Tortora, C; Covone, G; Capaccioli, M

    2015-01-01

    We present an integral field study of the internal structure, kinematics and stellar population of the almost edge-on, intermediate luminosity ($L_ {*}$) elliptical galaxy NGC~4697. We build extended 2-dimensional (2D) maps of the stellar kinematics and line-strengths of the galaxy up to $\\sim 0.7 $ effective radii (R$_{eff}$) using a mosaic of 8 VIMOS (VIsible Multi-Objects Spectrograph on the VLT) integral-field unit pointings. We find clear evidence for a rotation-supported structure along the major axis from the 2D kinematical maps, confirming the previous classification of this system as a `fast-rotator'. We study the correlations between the third and fourth Gauss-Hermite moments of the line-of-sight velocity distribution (LOSVD) $h_3$ and $h_4$ with the rotation parameter ($V/\\sigma$), and compare our findings to hydrodynamical simulations. We find remarkable similarities to predictions from gas-rich mergers. Based on photometry, we perform a bulge/disk decomposition and study the stellar population pr...

  17. Compact stellar systems in the polar ring galaxies NGC 4650A and NGC 3808B: Clues to polar disk formation

    CERN Document Server

    Ordenes-Briceño, Yasna; Puzia, Thomas H; Goudfrooij, Paul; Arnaboldi, Magda

    2016-01-01

    Polar ring galaxies (PRGs) are composed of two kinematically distinct and nearly orthogonal components, a host galaxy (HG) and a polar ring/disk (PR). The HG usually contains an older stellar population than the PR. The suggested formation channel of PRGs is still poorly constrained. Suggested options are merger, gas accretion, tidal interaction, or a combination of both. To constrain the formation scenario of PRGs, we study the compact stellar systems (CSSs) in two PRGs at different evolutionary stages: NGC 4650A with well-defined PR, and NGC 3808B, which is in the process of PR formation. We use archival HST/WFPC2 imaging. PSF-fitting techniques, and color selection criteria are used to select cluster candidates. Photometric analysis of the CSSs was performed to determine their ages and masses using stellar population models at a fixed metallicity. Both PRGs contain young CSSs ($< 1$ Gyr) with masses of up to 5$\\times$10$^6$M$_\\odot$, mostly located in the PR and along the tidal debris. The most massive ...

  18. The detection of spiral arm modulation in the stellar disk of an optically flocculent and an optically grand design galaxy

    CERN Document Server

    Puerari, I; Elmegreen, B G; Frogel, J A; Eskridge, P B; Puerari, Ivanio; Block, David L.; Elmegreen, Bruce G.; Frogel, Jay A.; Eskridge, Paul B.

    2000-01-01

    Two dimensional Fourier spectra of near-infrared images of galaxies provide a powerful diagnostic tool for the detection of spiral arm modulation in stellar disks. Spiral arm modulation may be understood in terms of interference patterns of outgoing and incoming density wave packets or modes. The brightness along a spiral arm will be increased where two wave crests meet and constructively interfere, but will be decreased where a wave crest and a wave trough destructively interfere. Spiral arm modulation has hitherto only been detected in grand design spirals (such as Messier 81). Spiral arm amplitude variations have the potential to become a powerful constraint for the study of galactic dynamics. We illustrate our method in two galaxies: NGC 4062 and NGC 5248. In both cases, we have detected trailing and leading m=2 waves with similar pitch angles. This suggests that the amplification mechanism is the WASER type II. In this mechanism, the bulge region reflects (rather than refracts) incoming waves with no cha...

  19. LEDA 074886: A remarkable rectangular-looking galaxy

    CERN Document Server

    Graham, Alister W; Forbes, Duncan A; Lisker, Thorsten; Moore, Ben; Janz, Joachim

    2012-01-01

    We report the discovery of an interesting and rare, rectangular-shaped galaxy. At a distance of 21 Mpc, the dwarf galaxy LEDA 074886 has an absolute R-band magnitude of -17.3 mag. Adding to this galaxy's intrigue is the presence of an embedded, edge-on stellar disk (of extent 2R_{e,disk} = 12 arcsec = 1.2 kpc) for which Forbes et al. reported V_rot/sigma ~ 1.4. We speculate that this galaxy may be the remnant of two (nearly edge-one) merged disk galaxies in which the initial gas was driven inward and subsequently formed the inner disk, while the stars at larger radii effectively experienced a dissipationless merger event resulting in this `emerald cut galaxy' having very boxy isophotes with a_4/a = -0.05 to -0.08 from 3 to 5 kpc. This galaxy suggests that knowledge from simulations of both `wet' and `dry' galaxy mergers may need to be combined to properly understand the various paths that galaxy evolution can take, with a particular relevance to blue elliptical galaxies.

  20. The CALIFA Survey Across the Hubble Sequence: How Galaxies Grow their Bulges and Disks

    Science.gov (United States)

    Gonzáez-Delgado, R. M.; García-Benito, R.; Pérez, E.; Cid Fernandes, R.; de Amorim, A. L.; Cortijo-Ferrero, C.; Lacerda, E. A. D.; López-Fernández, R.; Vale-Asari, R. L.; Sánchez, S.; Califa Collaboration

    2016-10-01

    We characterize in detail the radial structure of the stellar population properties of 300 galaxies in the nearby universe, observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, from spheroidal to spiral galaxies, ranging in stellar masses from M*˜109 to 7×1011 ⊙. We derive the stellar mass surface density (μ⋆), light-weighted and mass-weighted ages («log age»L, «log age»M), and mass-weighted metallicity («logZ⋆ »M), applying the spectral synthesis technique. We study the mean trends with galaxy stellar mass, M⋆, and morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). We confirm that more massive galaxies are more compact, older, more metal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble type: earlier types are more compact, older, and more metal rich for a given M⋆, which evidences that quenching is related to morphology, but not driven by mass.

  1. The CALIFA survey across the Hubble sequence: How galaxies grow their bulges and disks

    CERN Document Server

    Delgado, R M González; Pérez, E; Fernandes, R Cid; de Amorim, A L; Cortijo-Ferrero, C; Lacerda, E A D; Fernández, R López; Vale-Asari, N; Sánchez, S

    2015-01-01

    We characterize in detail the radial structure of the stellar population properties of 300 galaxies in the nearby universe, observed with integral field spectroscopy in the CALIFA survey. The sample covers a wide range of Hubble types, from spheroidal to spiral galaxies, ranging in stellar masses from $M_\\star \\sim 10^9$ to $7 \\times 10^{11}$ $M_\\odot$. We derive the stellar mass surface density ($\\mu_\\star$), light-weighted and mass-weighted ages ($\\langle {\\rm log}\\,age\\rangle _L$, $\\langle {\\rm log}\\,age\\rangle _M$), and mass-weighted metallicity ($\\langle {\\rm log}\\,Z_\\star\\rangle _M$), applying the spectral synthesis technique. We study the mean trends with galaxy stellar mass, $M_\\star$, and morphology (E, S0, Sa, Sb, Sbc, Sc and Sd). We confirm that more massive galaxies are more compact, older, more metal rich, and less reddened by dust. Additionally, we find that these trends are preserved spatially with the radial distance to the nucleus. Deviations from these relations appear correlated with Hubble...

  2. The Role of Major Gas-rich Mergers on the Evolution of Galaxies from the Blue Cloud to the Red Sequence

    Science.gov (United States)

    Guo, Rui; Hao, Cai-Na; Xia, X. Y.; Mao, Shude; Shi, Yong

    2016-07-01

    With the aim of exploring the fast evolutionary path from the blue cloud of star-forming galaxies to the red sequence of quiescent galaxies in the local universe, we select a local advanced merging infrared luminous and ultraluminous galaxy (adv-merger (U)LIRGs) sample and perform careful dust extinction corrections to investigate their positions in the star formation rate-M *, u - r, and NUV - r color-mass diagrams. The sample consists of 89 (U)LIRGs at the late merger stage, obtained from cross-correlating the Infrared Astronomical Satellite Point Source Catalog Redshift Survey and 1 Jy ULIRGs samples with the Sloan Digital Sky Survey DR7 database. Our results show that 74 % +/- 5 % of adv-merger (U)LIRGs are localized above the 1σ line of the local star-forming galaxy main sequence. We also find that all adv-merger (U)LIRGs are more massive than and as blue as the blue cloud galaxies after corrections for Galactic and internal dust extinctions, with 95 % +/- 2 % and 81 % +/- 4 % of them outside the blue cloud on the u - r and NUV - r color-mass diagrams, respectively. These results, combined with the short timescale for exhausting the molecular gas reservoir in adv-merger (U)LIRGs (3× {10}7 to 3× {10}8 years), imply that the adv-merger (U)LIRGs are likely at the starting point of the fast evolutionary track previously proposed by several groups. While the number density of adv-merger (U)LIRGs is only ˜ 0.1 % of the blue cloud star-forming galaxies in the local universe, this evolutionary track may play a more important role at high redshift.

  3. SUPERLUMINOUS SPIRAL GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Ogle, Patrick M.; Lanz, Lauranne; Nader, Cyril; Helou, George, E-mail: ogle@ipac.caltech.edu [IPAC, California Institute of Technology, Mail Code 220-6, Pasadena, CA 91125 (United States)

    2016-02-01

    We report the discovery of spiral galaxies that are as optically luminous as elliptical brightest cluster galaxies, with r-band monochromatic luminosity L{sub r} = 8–14L* (4.3–7.5 × 10{sup 44} erg s{sup −1}). These super spiral galaxies are also giant and massive, with diameter D = 57–134 kpc and stellar mass M{sub stars} = 0.3–3.4 × 10{sup 11}M{sub ⊙}. We find 53 super spirals out of a complete sample of 1616 SDSS galaxies with redshift z < 0.3 and L{sub r} > 8L*. The closest example is found at z = 0.089. We use existing photometry to estimate their stellar masses and star formation rates (SFRs). The SDSS and Wide-field Infrared Survey Explorer colors are consistent with normal star-forming spirals on the blue sequence. However, the extreme masses and rapid SFRs of 5–65 M{sub ⊙} yr{sup −1} place super spirals in a sparsely populated region of parameter space, above the star-forming main sequence of disk galaxies. Super spirals occupy a diverse range of environments, from isolation to cluster centers. We find four super spiral galaxy systems that are late-stage major mergers—a possible clue to their formation. We suggest that super spirals are a remnant population of unquenched, massive disk galaxies. They may eventually become massive lenticular galaxies after they are cut off from their gas supply and their disks fade.

  4. Bar Diagnostics in Edge-On Spiral Galaxies. III. N-Body Simulations of Disks

    CERN Document Server

    Bureau, M

    2004-01-01

    Present in over 45% of local spirals, boxy and peanut-shaped bulges are generally interpreted as edge-on bars and may represent a key phase in the evolution of bulges. Aiming to test such claims, the kinematic properties of self-consistent 3D N-body simulations of bar-unstable disks are studied. Using Gauss-Hermite polynomials to describe the stellar kinematics, a number of characteristic bar signatures are identified in edge-on disks: 1) a major-axis light profile with a quasi-exponential central peak and a plateau at moderate radii (Freeman Type II profile); 2) a ``double-hump'' rotation curve; 3) a sometime flat central velocity dispersion peak with a plateau at moderate radii and occasional local central minimum and secondary peak; 4) an h3-V correlation over the projected bar length. All those kinematic features are spatially correlated and can easily be understood from the orbital structure of barred disks. They thus provide a reliable and easy-to-use tool to identify edge-on bars. Interestingly, they a...

  5. Mass and metal ejection efficiency in disk galaxies driven by young stellar clusters of nuclear starburst

    CERN Document Server

    Rodriguez-Gonzalez, A; Raga, A C; Colin, P

    2011-01-01

    We present results from models of galactic winds driven by energy injected by nuclear starbursts. The total energy of the starburst is provided by young central stellar clusters and parts of the galactic interstellar medium are pushed out as part of the galactic wind (in some cases the galactic wind contains an important part of the metals produced in the new generation of stars). We have performed adiabatic and radiative 3D N-Body/Smooth Particle Hydrodynamics simulations of galactic winds using the GADGET-2 code. The numerical models cover a wide range of starburst (from $\\sim10^2$ to $\\sim10^7$ M$_\\odot$) and galactic gas masses (from $\\sim6\\times10^6$ to $\\sim10^{11}$ M$_\\odot$). The concentrated central starburst regions are an efficient engine for producing of the mass and metal loss in galaxies, and also for driving the metal redistribution in the galaxies.

  6. NO EVIDENCE FOR CLASSICAL CEPHEIDS AND A NEW DWARF GALAXY BEHIND THE GALACTIC DISK

    Energy Technology Data Exchange (ETDEWEB)

    Pietrukowicz, P.; Udalski, A.; Szymański, M. K.; Soszyński, I.; Pietrzyński, G.; Wyrzykowski, Ł.; Poleski, R.; Ulaczyk, K.; Skowron, J.; Mróz, P.; Pawlak, M.; Kozłowski, S. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

    2015-11-10

    Based on data from the ongoing OGLE Galaxy Variability Survey (OGLE GVS), we have verified observed properties of stars detected by the near-infrared VVV survey in a direction near the Galactic plane at longitude l ≈ −27° and recently tentatively classified as classical Cepheids belonging to, hence claimed, a dwarf galaxy at a distance of about 90 kpc from the Galactic Center. Three of four stars are detected in the OGLE GVS I-band images. We show that two of the objects are not variable at all, and the third one with a period of 5.695 days and a nearly sinusoidal light curve of an amplitude of 0.5 mag cannot be a classical Cepheid and is very likely a spotted object. These results together with a very unusual shape of the K{sub s}-band light curve of the fourth star indicate that it is very likely that none of them is a Cepheid and, thus there is no evidence for a background dwarf galaxy. Our observations show that great care must be taken when classifying objects by their low-amplitude close-to-sinusoidal near-infrared light curves, especially with a small number of measurements. We also provide a sample of high-amplitude spotted stars with periods of a few days that can mimic pulsations and even eclipses.

  7. No Evidence for Classical Cepheids and a New Dwarf Galaxy Behind the Galactic Disk

    CERN Document Server

    Pietrukowicz, P; Szymanski, M K; Soszynski, I; Pietrzynski, G; Wyrzykowski, L; Poleski, R; Ulaczyk, K; Skowron, J; Mroz, P; Pawlak, M; Kozlowski, S

    2015-01-01

    Based on data from the ongoing OGLE Galaxy Variability Survey (OGLE GVS) we have verified observed properties of stars detected by the near-infrared VVV survey in a direction near the Galactic plane at longitude l~-27 deg and recently tentatively classified as classical Cepheids belonging to a, hence claimed, dwarf galaxy at a distance of about 90 kpc from the Galactic Center. Three of four stars are detected in the OGLE GVS I-band images. We show that two of the objects are not variable at all and the third one with a period of 5.695 d and a nearly sinusoidal light curve of an amplitude of 0.5 mag cannot be a classical Cepheid and is very likely a spotted object. These results together with a very unusual shape of the Ks-band light curve of the fourth star indicate that very likely none of them is a Cepheid and, thus, there is no evidence for a background dwarf galaxy. Our observations show that a great care must be taken when classifying objects by their low-amplitude close-to-sinusoidal near-infrared light...

  8. DiskFit: a code to fit simple non-axisymmetric galaxy models either to photometric images or to kinematic maps

    CERN Document Server

    Sellwood, J A

    2015-01-01

    This posting announces public availability of version 1.2 of the DiskFit software package developed by the authors, which may be used to fit simple non-axisymmetric models either to images or to velocity fields of disk galaxies. Here we give an outline of the capability of the code and provide the link to downloading executables, the source code, and a comprehensive on-line manual. We argue that in important respects the code is superior to rotcur for fitting kinematic maps and to galfit for fitting multi-component models to photometric images.

  9. The Relationship between the Dense Neutral and Diffuse Ionized Gas in the Thick Disks of Two Edge-on Spiral Galaxies

    Science.gov (United States)

    Rueff, Katherine M.; Howk, J. Christopher; Pitterle, Marissa; Hirschauer, Alec S.; Fox, Andrew J.; Savage, Blair D.

    2013-03-01

    We present high-resolution, optical images (BVI + Hα) of the multiphase interstellar medium (ISM) in the thick disks of the edge-on spiral galaxies NGC 4013 and NGC 4302. Our images from the Hubble Space Telescope (HST), Large Binocular Telescope, and WIYN 3.5 m telescope reveal an extensive population of filamentary dust absorption seen to z ~2-2.5 kpc. Many of these dusty thick disk structures have characteristics reminiscent of molecular clouds found in the Milky Way disk. Our Hα images show that the extraplanar diffuse ionized gas (DIG) in these galaxies is dominated by a smooth, diffuse component. The strongly filamentary morphologies of the dust absorption have no counterpart in the smoothly distributed Hα emission. We argue that the thick disk DIG and dust-bearing filaments trace physically distinct phases of the thick disk ISM, the latter tracing a dense, warm or cold neutral medium. The dense, dusty matter in the thick disks of spiral galaxies is largely tracing matter ejected from the thin disk via energetic feedback from massive stars. The high densities of the gas may be a result of converging gas flows. This dense material fuels some thick disk star formation, as evidenced by the presence of thick disk H II regions. Based on observations obtained with the NASA/ESA Hubble Space Telescope operated at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Also, based on data acquired using the Large Binocular Telescope (LBT). The LBT is an international collaboration among institutions in the US, Italy, and Germany. LBT Corporation partners are the University of Arizona, on behalf of the Arizona University System; Instituto Nazionale do Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute of Potsdam, and Heidelberg University; Ohio State University, and the Research Corporation, on

  10. Surface brightness profiles of blue compact dwarf galaxies in the GOODS-N and GOODS-S field

    CERN Document Server

    Lian, Jianhui; Jiang, Ning; Yan, Wei; Gao, Yulong

    2016-01-01

    We investigate the structural properties of the underlying hosts of 34 blue compact dwarf (BCD) galaxies with deep near-infrared (NIR) photometry. The BCD sample is selected from the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey in the Great observatories origins Deep Survey North and South fields. We extract the surface brightness profile (SBP) in the optical F 435W and NIR F 160W bands. The SBPs of BCDs in the H band reach 26 mag arcsec^-2 at the 3\\sigma level, which is so far the deepest NIR imaging of BCDs. Then we fit the SBPs with one- and two- component Sersic models. About half of the BCDs favour the two-component model which significantly improves the fit quality. The effective radii of the underlying hosts of BCDs in the B band are smaller than those of early-type dwarfs (dEs) and dwarf irregulars at a fixed luminosity. This discrepancy is similar to findings in many previous works. However, the difference in structural parameters between BCDs and other dwarf galaxies seems to be less sig...

  11. Small-scale properties of atomic gas in extended disks of galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Borthakur, Sanchayeeta; Heckman, Timothy M. [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); Momjian, Emmanuel [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); York, Donald G. [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Bowen, David V. [Princeton University Observatory, Peyton Hall, Ivy Lane, Princeton, NJ 08544 (United States); Yun, Min S.; Tripp, Todd M., E-mail: sanch@pha.jhu.edu [Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)

    2014-11-01

    We present high-resolution H I 21 cm observations with the Karl G. Jansky Very Large Array for three H I rich galaxies in absorption against radio quasars. Our sample contains six sightlines with impact parameters from 2.6 to 32.4 kpc. We detected a narrow H I absorber of FWHM 1.1 km s{sup –1} at 444.5 km s{sup –1} toward SDSS J122106.854+454852.16 probing the dwarf galaxy UCG 7408 at an impact parameter of 2.8 kpc. The absorption feature was barely resolved and its width corresponds to a maximum kinetic temperature, T{sub k} ≈ 26 K. We estimate a limiting peak optical depth of 1.37 and a column density of 6 × 10{sup 19} cm{sup –2}. The physical extent of the absorber is 0.04 kpc{sup 2} and covers ∼25%-30% of the background source. A comparison between the emission and absorption strengths suggests the cold-to-total H I column density in the absorber is ∼30%. Folding in the covering fraction, the cold-to-total H I mass is ∼10%. This suggest that condensation of warm H I (T{sub s} ∼ 1000 K) to cold phase (T{sub s} < 100 K) is suppressed in UGC 7408. The unusually low temperature of the H I absorber also indicates inefficiency in condensation of atomic gas into molecular gas. The suppression in condensation is likely to be the result of low metal content in this galaxy. The same process might explain the low efficiency of star formation in dwarf galaxies despite their huge gas reservoirs. We report the non-detection of H I in absorption in five other sightlines. This indicates that either the cold gas distribution is highly patchy or the gas is much warmer (T{sub s} > 1000 K) toward these sightlines.

  12. Giant Molecular Cloud Formation in Disk Galaxies: Characterizing Simulated versus Observed Cloud Catalogues

    CERN Document Server

    Benincasa, Samantha M; Pudritz, Ralph E; Wadsley, James

    2013-01-01

    We present the results of a study of simulated Giant Molecular Clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10^4 Msun and 10^7 Msun. We compare our simulated cloud population to two observational surveys; The Boston University- Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary - a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud- cloud gravitational encounters. We also find that the rate at which potentially s...

  13. Exploring the Interstellar Media of Optically Compact Dwarf Galaxies

    CERN Document Server

    Most, Hans P; Salzer, John J; Rosenberg, Jessica J; Engstrom, Eric; Fliss, Palmer

    2013-01-01

    We present new Very Large Array HI spectral line, archival Sloan Digital Sky Survey, and archival Spitzer Space Telescope imaging of eight star-forming blue compact dwarf galaxies that were selected to be optically compact (optical radii less than 1 kpc). These systems have faint blue absolute magnitudes (M_B >= -17), ongoing star formation (based on emission-line selection by the H alpha or [OIII] lines), and are nearby (mean velocity = 3315 km/s = 45 Mpc). One galaxy in the sample, ADBS 113845+2008, is found to have an HI halo that extends 58 r-band scale lengths from its stellar body. In contrast, the rest of the sample galaxies have HI radii to optical-scale-length ratios ranging from 9.3 to 26. The size of the HI disk in the "giant disk" dwarf galaxy ADBS 113845+2008 appears to be unusual as compared to similarly compact stellar populations.

  14. A Gemini/GMOS study of the physical conditions and kinematics of the blue compact dwarf galaxy Mrk 996

    CERN Document Server

    Telles, Eduardo; Izotov, Yuri I; Carrasco, Eleazar Rodrigo

    2013-01-01

    We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph (GMOS) of the unusual blue compact dwarf (BCD) galaxy Mrk 996. We show through velocity and dispersion maps, emission-line intensity and ratio maps, and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties. From the maps, we can spatially distinguish a very dense high-ionization zone with broad lines in the nuclear region, and a less dense low-ionization zone with narrow lines in the circumnuclear region. Four kinematically distinct systems of lines are identified in the integrated spectrum of Mrk 996, suggesting stellar wind outflows from a population of Wolf-Rayet (WR) stars in the nuclear region, superposed on an underlying rotation pattern. From the intensities of the blue and red bumps, we derive a population of $\\sim$473 late nitrogen (WNL) stars and $\\sim$98 early carbon (WCE) stars in the nucleus of Mrk ...

  15. Spectroastrometry of rotating gas disks for the detection of supermassive black holes in galactic nuclei. II. Application to the galaxy Centaurus A (NGC 5128)

    OpenAIRE

    Gnerucci, A.; Marconi, A.; Capetti, A.; Axon, D. J.; Robinson, A.; Neumayer, N.

    2011-01-01

    We measure the black hole mass in the nearby active galaxy Centaurus A (NGC 5128) using a new method based on spectroastrometry of a rotating gas disk. The spectroastrometric approach consists in measuring the photocenter position of emission lines for different velocity channels. In a previous paper we focused on the basic methodology and the advantages of the spectroastrometric approach with a detailed set of simulations demonstrating the possibilities for black hole mass measurements going...

  16. Small-scale Properties of Atomic Gas in Extended Disks of Galaxies

    CERN Document Server

    Borthakur, Sanchayeeta; Heckman, Timothy M; York, Donald G; Bowen, David V; Yun, Min S; Tripp, Todd M

    2014-01-01

    We present high-resolution HI 21 cm observations with the Karl G. Jansky Very Large Array (VLA) for three HI rich galaxies in absorption against radio quasars. Our sample contains six sightlines with impact parameters from 2.6 to 32.4 kpc. We detected a narrow HI absorber of FWHM 1.1 km/s at 444.5 km/s towards J122106.854+454852.16 probing the dwarf galaxy UCG 7408 at an impact parameter of 2.8 kpc. The absorption feature was barely resolved and its width corresponds to a maximum kinetic temperature, $\\rm T_k \\approx 26~K$. We estimate a limiting peak optical depth of 1.37 and a column density of $\\rm 6\\times 10^{19}~cm^{-2}$. The physical extent of the absorber is $\\rm 0.04~kpc^2$ and covers $\\sim$25-30\\% of the background source. A comparison between the emission and absorption strengths suggests the cold-to-total HI column density in the absorber is ~30%. Folding in the covering fraction, the cold-to-total HI mass is ~10%. This suggest that condensation of warm HI ($\\rm T_s\\sim 1000~K$) to cold phase ($\\rm...

  17. Strong Evidence for the Density-wave Theory of Spiral Structure in Disk Galaxies

    CERN Document Server

    Pour-Imani, Hamed; Kennefick, Julia; Davis, Benjamin L; Shields, Douglas W; Abdeen, Mohamed Shameer

    2016-01-01

    The density-wave theory of galactic spiral-arm structure makes a striking prediction that the pitch angle of spiral arms should vary with the wavelength of the galaxy's image. The reason is that stars are born in the density wave but move out of it as they age. They move ahead of the density wave inside the co-rotation radius, and fall behind outside of it, resulting in a tighter pitch angle at wavelengths that image stars (optical and near-infrared) than those that are associated with star formation (far-infrared and ultraviolet). In this study we combined large sample size with wide range of wavelengths, from the ultraviolet to the infrared to investigate this issue. For each galaxy we used an optical wavelength image (B-band: 445 nm) and images from the Spitzer Space Telescope at two infrared wavelengths (infrared: 3.6 and 8.0 {\\mu}m) and we measured the pitch angle with the 2DFFT and Spirality codes. We find that the B-band and 3.6 {\\mu}m images have smaller pitch angles than the infrared 8.0 {\\mu}m image...

  18. An Intermittent Star Formation History in a "Normal" Disk Galaxy: The Milky Way.

    Science.gov (United States)

    Rocha-Pinto; Scalo; Maciel; Flynn

    2000-03-10

    The star formation rate history of the Milky Way is derived using the chromospheric age distribution for 552 stars in the solar neighborhood. The stars' sample birth sites are distributed over a very large range of distances because of orbital diffusion and so give an estimate of the global star formation rate history. The derivation incorporates the metallicity dependence of chromospheric emission at a given age and corrections to account for incompleteness, scale height-age correlations, and stellar evolutionary effects. We find fluctuations in the global star formation rate with amplitudes greater than a factor of 2-3 on timescales less than 0.2-1 Gyr. The actual history is likely to be more bursty than found here because of the smearing effect of age uncertainties. There is some evidence for a slow secular increase in the star formation rate, perhaps a record of the accumulation history of our Galaxy. A smooth, nearly constant star formation rate history is strongly ruled out, confirming the result first discovered by Barry using a smaller sample and a different age calibration. This result suggests that galaxies can fluctuate coherently on large scales.

  19. Chemo -- dynamical, multi -- fragmented SPH code for evolution of star forming disk galaxies

    Science.gov (United States)

    Berczik, P.

    The problem of chemical and dynamical evolution of galaxies is one of the most attracting and complex problems of modern astrophysics. Within the framework of the given paper the standard dynamic Smoothed Particle Hydrodynamics (SPH) code (Monaghan J.J. 1992, ARAA, 30, 543) is noticeably expanded. Our work concernes with the changes and incorporation of new ideas into the algorithmic inclusion of Star Formation (SF) and Super Novae (SN) explosions in SPH (Berczik P. & Kravchuk S.G., 1996, ApSpSci, 245, 27). The proposed energy criterion for definition of a place and efficiency of SF results in the successfully explain Star Formation History (SFH) in isolated galaxies of different types. On the base of original ideas we expand a code in a more realistic way of the description of effects of return of a hot, chemical enriched gas in Interstellar Matter (ISM). In addition to the account of SNII, we offer the self-agreed account of SNIa and PN. This allows to describe not only the ISM content of O^16 but also the content of Fe^56 . This model will allow to investigate adequately also a well known G - dwarf problem.

  20. THE RISE AND FALL OF THE STAR FORMATION HISTORIES OF BLUE GALAXIES AT REDSHIFTS 0.2 < z < 1.4

    Energy Technology Data Exchange (ETDEWEB)

    Pacifici, Camilla [Yonsei University Observatory, Yonsei University, Seoul 120-749 (Korea, Republic of); Kassin, Susan A.; Gardner, Jonathan P. [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Weiner, Benjamin [Steward Observatory, 933 North Cherry Street, University of Arizona, Tucson, AZ 85721 (United States); Charlot, Stephane [UPMC-CNRS, UMR7095, Institut d' Astrophysique de Paris, F-75014 Paris (France)

    2013-01-01

    Popular cosmological scenarios predict that galaxies form hierarchically from the merger of many progenitors, each with their own unique star formation history (SFH). We use a sophisticated approach to constrain the SFHs of 4517 blue (presumably star-forming) galaxies with spectroscopic redshifts in the range 0.2 < z < 1.4 from the All-Wavelength Extended Groth Strip International Survey. This consists in the Bayesian analysis of the observed galaxy spectral energy distributions with a comprehensive library of synthetic spectra assembled using realistic, hierarchical star formation, and chemical enrichment histories from cosmological simulations. We constrain the SFH of each galaxy in our sample by comparing the observed fluxes in the B, R, I, and K{sub s} bands and rest-frame optical emission-line luminosities with those of one million model spectral energy distributions. We explore the dependence of the resulting SFHs on galaxy stellar mass and redshift. We find that the average SFHs of high-mass galaxies rise and fall in a roughly symmetric bell-shaped manner, while those of low-mass galaxies rise progressively in time, consistent with the typically stronger activity of star formation in low-mass compared to high-mass galaxies. For galaxies of all masses, the star formation activity rises more rapidly at high than at low redshift. These findings imply that the standard approximation of exponentially declining SFHs widely used to interpret observed galaxy spectral energy distributions may not be appropriate to constrain the physical parameters of star-forming galaxies at intermediate redshifts.

  1. THE EPOCH OF DISK SETTLING: z {approx} 1 TO NOW

    Energy Technology Data Exchange (ETDEWEB)

    Kassin, Susan A.; Gardner, Jonathan P. [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Weiner, Benjamin J.; Willmer, C. N. A. [Steward Observatory, University of Arizona, Tucson, AZ (United States); Faber, S. M.; Guhathakurta, Puragra; Koo, David C. [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Coil, Alison L. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Devriendt, Julien [Department of Physics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Dutton, Aaron A. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Metevier, A. J. [Department of Physics and Astronomy, Sonoma State University, 1801 East Cotati Avenue, Rohnert Park, CA 94928 (United States); Noeske, Kai G. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Primack, Joel R., E-mail: susan.kassin@nasa.gov [Department of Physics, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2012-10-20

    We present evidence from a sample of 544 galaxies from the DEEP2 Survey for evolution of the internal kinematics of blue galaxies with stellar masses ranging 8.0 < log M {sub *}(M {sub Sun }) < 10.7 over 0.2 < z < 1.2. DEEP2 provides galaxy spectra and Hubble imaging from which we measure emission-line kinematics and galaxy inclinations, respectively. Our large sample allows us to overcome scatter intrinsic to galaxy properties in order to examine trends in kinematics. We find that at a fixed stellar mass, galaxies systematically decrease in disordered motions and increase in rotation velocity and potential well depth with time. Massive galaxies are the most well ordered at all times examined, with higher rotation velocities and less disordered motions than less massive galaxies. We quantify disordered motions with an integrated gas velocity dispersion corrected for beam smearing ({sigma} {sub g}). It is unlike the typical pressure-supported velocity dispersion measured for early type galaxies and galaxy bulges. Because both seeing and the width of our spectral slits comprise a significant fraction of the galaxy sizes, {sigma} {sub g} integrates over velocity gradients on large scales which can correspond to non-ordered gas kinematics. We compile measurements of galaxy kinematics from the literature over 1.2 < z < 3.8 and do not find any trends with redshift, likely for the most part, because these data sets are biased toward the most highly star-forming systems. In summary, over the last {approx}8 billion years since z = 1.2, blue galaxies evolve from disordered to ordered systems as they settle to become the rotation-dominated disk galaxies observed in the universe today, with the most massive galaxies being the most evolved at any time.

  2. The Century Survey Galactic Halo Project III: A Complete 4300 deg^2 Survey of Blue Horizontal Branch Stars in the Metal-Weak Thick Disk and Inner Halo

    CERN Document Server

    Brown, Warren R; Wilhelm, Ronald; Prieto, Carlos Allende; Geller, Margaret J; Kenyon, Scott J; Kurtz, Michael J

    2007-01-01

    We present a complete spectroscopic survey of 2414 2MASS-selected blue horizontal branch (BHB) candidates selected over 4300 deg^2 of the sky. We identify 655 BHB stars in this non-kinematically selected sample. We calculate the luminosity function of field BHB stars and find evidence for very few hot BHB stars in the field. The BHB stars located at a distance from the Galactic plane |Z|<4 kpc trace what is clearly a metal-weak thick disk population, with a mean metallicity of [Fe/H]= -1.7, a rotation velocity gradient of dv_{rot}/d|Z|= -28+-3.4 km/s in the region |Z|<6 kpc, and a density scale height of h_Z= 1.26+-0.1 kpc. The BHB stars located at 5<|Z|<9 kpc are a predominantly inner-halo population, with a mean metallicity of [Fe/H]= -2.0 and a mean Galactic rotation of -4+-31 km/s. We infer the density of halo and thick disk BHB stars is 104+-37 kpc^-3 near the Sun, and the relative normalization of halo to thick-disk BHB stars is 4+-1% near the Sun.

  3. Star Formation Rates in Low Surface Brightness Galaxies

    NARCIS (Netherlands)

    Pickering, T. E.; Impey, C. D.; van Gorkom, J.; Bothun, G. D.

    1994-01-01

    The low surface brightness (LSB) disk galaxies found in recent surveys (e.g.,\\ Schombert et al. 1992, AJ, 103, 1107) tend to be blue and gas rich. These properties along with their low mean surface luminosity and H i densities imply an inefficient mode of star formation. The Hα images that we presen

  4. FIR extended emission from cold gas and dust in Blue Compact Dwarf Galaxies: the anomalous cases of POX 186 and UM 461

    CERN Document Server

    Doublier, Vanessa

    2016-01-01

    FIR observation of BCD galaxies with Herschel has revealed a wealth of new insights in these objects which are thought to resemble high-redshift forming galaxies. Dust and cold gas showed to be colder, in more or less quantities than expected and of uncertain origin. However, not unlike in the local universe, not all the dust or the cold gas is accounted for, making it more challenging. SPICA and its factor 10 to 100 in sensitivity will allow to image the faint extended cold gas/dusty disks in BCDGs in addition to detect faint C and O lines only marginally or not at all detected by Herschel/

  5. Star Formation in Disk Galaxies. III. Does stellar feedback result in cloud death?

    CERN Document Server

    Tasker, Elizabeth J; Pudritz, Ralph

    2015-01-01

    Stellar feedback, star formation and gravitational interactions are major controlling forces in the evolution of Giant Molecular Clouds (GMCs). To explore their relative roles, we examine the properties and evolution of GMCs forming in an isolated galactic disk simulation that includes both localised thermal feedback and photoelectric heating. The results are compared with the three previous simulations in this series which consists of a model with no star formation, star formation but no form of feedback and star formation with photoelectric heating in a set with steadily increasing physical effects. We find that the addition of localised thermal feedback greatly suppresses star formation but does not destroy the surrounding GMC, giving cloud properties closely resembling the run in which no stellar physics is included. The outflows from the feedback reduce the mass of the cloud but do not destroy it, allowing the cloud to survive its stellar children. This suggests that weak thermal feedback such as the low...

  6. Giant Molecular Cloud Formation in Disk Galaxies: Characterizing Simulated versus Observed Cloud Catalogs

    Science.gov (United States)

    Benincasa, Samantha M.; Tasker, Elizabeth J.; Pudritz, Ralph E.; Wadsley, James

    2013-10-01

    We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 104 M ⊙ and 107 M ⊙. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n thresh >= 104 cm-3—is 3% per 10 Myr, in clouds of roughly 106 M ⊙. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.

  7. GIANT MOLECULAR CLOUD FORMATION IN DISK GALAXIES: CHARACTERIZING SIMULATED VERSUS OBSERVED CLOUD CATALOGS

    Energy Technology Data Exchange (ETDEWEB)

    Benincasa, Samantha M.; Pudritz, Ralph E.; Wadsley, James [Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 (Canada); Tasker, Elizabeth J. [Department of Physics, Faculty of Science, Hokkaido University, Kita-ku, Sapporo 060-0810 (Japan)

    2013-10-10

    We present the results of a study of simulated giant molecular clouds (GMCs) formed in a Milky Way-type galactic disk with a flat rotation curve. This simulation, which does not include star formation or feedback, produces clouds with masses ranging between 10{sup 4} M{sub ☉} and 10{sup 7} M{sub ☉}. We compare our simulated cloud population to two observational surveys: the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey and the BIMA All-Disk Survey of M33. An analysis of the global cloud properties as well as a comparison of Larson's scaling relations is carried out. We find that simulated cloud properties agree well with the observed cloud properties, with the closest agreement occurring between the clouds at comparable resolution in M33. Our clouds are highly filamentary—a property that derives both from their formation due to gravitational instability in the sheared galactic environment, as well as to cloud-cloud gravitational encounters. We also find that the rate at which potentially star-forming gas accumulates within dense regions—wherein n{sub thresh} ≥ 10{sup 4} cm{sup –3}—is 3% per 10 Myr, in clouds of roughly 10{sup 6} M{sub ☉}. This suggests that star formation rates in observed clouds are related to the rates at which gas can be accumulated into dense subregions within GMCs via filamentary flows. The most internally well-resolved clouds are chosen for listing in a catalog of simulated GMCs—the first of its kind. The cataloged clouds are available as an extracted data set from the global simulation.

  8. VLT/X-shooter observations of the low-metallicity blue compact dwarf galaxy PHL 293B including a luminous blue variable star

    Science.gov (United States)

    Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Henkel, C.

    2011-09-01

    Context. We present VLT/X-shooter spectroscopic observations in the wavelength range λλ3000-23 000 Å of the extremely metal-deficient blue compact dwarf (BCD) galaxy PHL 293B containing a luminous blue variable (LBV) star and compare them with previous data. Aims: This BCD is one of the two lowest-metallicity galaxies where LBV stars were detected, allowing us to study the LBV phenomenon in the extremely low metallicity regime. Methods: We determine abundances of nitrogen, oxygen, neon, sulfur, argon, and iron by analyzing the fluxes of narrow components of the emission lines using empirical methods and study the properties of the LBV from the fluxes and widths of broad emission lines. Results: We derive an interstellar oxygen abundance of 12+log O/H = 7.71 ± 0.02, which is in agreement with previous determinations. The observed fluxes of narrow Balmer, Paschen and Brackett hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value C(Hβ) = 0.225. This implies that the star-forming region observed in the optical range is the only source of ionisation and there is no additional source of ionisation that is seen in the NIR range but is hidden in the optical range. We detect three v = 1-0 vibrational lines of molecular hydrogen. Their flux ratios and non-detection of v = 2-1 and 3-1 emission lines suggest that collisional excitation is the main source producing H2 lines. For the LBV star in PHL 293B we find broad emission with P Cygni profiles in several Balmer hydrogen emission lines and for the first time in several Paschen hydrogen lines and in several He i emission lines, implying temporal evolution of the LBV on a time scale of 8 years. The Hα luminosity of the LBV star is by one order of magnitude higher than the one obtained for the LBV star in NGC 2363 ≡ Mrk 71 which has a slightly higher metallicity 12+logO/H = 7.87. The terminal velocity of the stellar wind in the low-metallicity LBV of PHL293

  9. Interplay between Dark Matter and Galactic Structure in Disk and Oblate Elliptical Galaxies

    Indian Academy of Sciences (India)

    Euaggelos E. Zotos; Nicolaos D. Caranicolas

    2014-12-01

    Understanding the regular or chaotic nature of orbits in galaxies is undoubtedly an issue of great importance. We determine the character of orbits of stars moving in the meridional plane (, ) of an axially symmetric time-independent galactic model with a spherical central nucleus, and a flat biaxial oblate dark matter halo component. In particular, we try to reveal the influence of the fractional portion of dark matter on the structure and also on the different families of orbits of the galaxy, by monitoring how the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families evolve when the ratio of dark matter to luminous mass varies. The smaller alignment index (SALI) was computed by numerically integrating the equations of motion as well as the variational equations to extensive samples of orbits in order to distinguish between ordered and chaotic motion. In addition, a method based on the concept of spectral dynamics that utilizes the Fourier transform of the time series of each coordinate is used to identify the various families of regular orbits and also to recognize the secondary resonances that bifurcate from them. The investigation is carried out both in the physical (, ) and the phase (, $\\dot{R}$) space for a better understanding of the orbital properties of the system. The numerical computations reveal that in both cases, the fractional portion of dark matter influences more or less, the overall orbital structure of the system. It was observed however, that the evolution of the percentages of all types of orbits as a function of the fractional portion of dark matter strongly depends on the particular type of space (physical or phase) in which the initial conditions of orbits are launched. The results are compared with the similar earlier work.

  10. The star-formation history of low-mass disk galaxies: a case study of NGC\\,300

    CERN Document Server

    Kang, Xiaoyu; Chang, Ruixiang; Wang, Lang; Cheng, Liantao

    2015-01-01

    Since NGC300 is a bulge-less, isolated low-mass galaxy and has not experienced radial migration during its evolution history, it can be treated as an ideal laboratory to test simple galactic chemical evolution models. By assuming its disk forms gradually from continuous accretion of primordial gas and including the gas-outflow process, we construct a simple chemical evolution model for NGC300 to build a bridge between its SFH and its observed data, especially the present-day radial profiles and global observed properties (e.g., cold gas mass, star-formation rate and metallicity). By means of comparing the model predictions with the corresponding observations, we adopt the classical $\\chi^{2}$ methodology to find out the best combination of free parameters $a$, $b$ and $b_{\\rm out}$. Our results show that, by assuming an inside-out formation scenario and an appropriate outflow rate, our model reproduces well most of the present-day observational values, not only the radial profiles but also the global observat...

  11. Transition between order and chaos in a composite disk galaxy model with a massive nucleus and a dark matter halo

    CERN Document Server

    Caranicolas, Nicolaos D

    2012-01-01

    We investigate the transition from regular to chaotic motion in a composite galaxy model with a disk-halo, a massive dense nucleus and a dark halo component. We obtain relationships connecting the critical value of the mass of the nucleus or the critical value of the angular momentum, with the mass of the dark halo, where the transition from regular motion to chaos occurs. We also present 3D diagrams connecting the mass of nucleus the energy and the percentage of stars that can show chaotic motion. The fraction of the chaotic orbits observed in the phase plane, as a function of the mass of the dark halo is also computed. We use a semi-numerical method, that is a combination of theoretical and numerical procedure. The theoretical results obtained using the version 8.0 of the Mathematica package, while all the numerical calculations were made using a Bulirsch-Stoer FORTRAN routine in double precision. The results can be obtained in semi-numerical or numerical form and give good description for the connection of...

  12. CARMA Survey Toward Infrared-bright Nearby Galaxies (STING) II: Molecular Gas Star Formation Law and Depletion Time Across the Blue Sequence

    CERN Document Server

    Rahman, Nurur; Xue, Rui; Wong, Tony; Leroy, Adam K; Walter, Fabian; Bigiel, Frank; Rosolowsky, Erik; Fisher, David B; Vogel, Stuart N; Blitz, Leo; West, Andrew A; Ott, Juergen

    2011-01-01

    We present an analysis of the relationship between molecular gas and current star formation rate surface density at sub-kpc and kpc scales in a sample of 14 nearby star-forming galaxies. Measuring the relationship in the bright, high molecular gas surface density ($\\Shtwo\\gtrsim$20 \\msunpc) regions of the disks to minimize the contribution from diffuse extended emission, we find an approximately linear relation between molecular gas and star formation rate surface density, $\

  13. Star formation and nuclear activity in the blue early-type galaxy NGC 5373

    Science.gov (United States)

    Zaidi, Tayeb; Miller, Brendan P.; Gallo, Elena; Alfvin, Erik; Martinkus, Charlotte; Molter, Edward

    2015-01-01

    We present new optical and X-ray observations of NGC 5373, an isolated star-forming elliptical that has a stellar mass of 7e10 solar and lies at a distance of 175 Mpc. Our B and R band Magellan IMACS imaging substantially improves on SDSS resolution and sensitivity, enabling accurate modeling of the galaxy surface brightness profile. As expected from its mass, NGC 5373 is a core galaxy with a best-fit Sersic profile of n~3.8; no prominent tidal tails or shells are found, although there are slight residual asymmetries. The H-alpha emission in the SDSS spectrum is narrow, and the line ratios confirm a star-forming classification in the BPT diagram, near the transition/composite line. The star formation rate is about 6 solar masses per year, making NGC 5373 an extreme outlier relative to typical local early-type galaxies of similar mass. Our 50 ks Chandra ACIS-S exposure provides a clear detection of a central X-ray source, with a hardness ratio consistent with a power-law photon index of 2.0+/-0.5. The unabsorbed luminosity is Lx = 2e40 erg/s over 0.3-8 keV. Comparison with a MARX simulated point spread function suggests the central source may be extended, for example due to contributions from one or more unresolved high-mass X-ray binaries, as might be present given the high star formation rate. For a black hole of 1.6e8 solar masses as predicted from scaling relations, Lx/Ledd is then around 1e-6 (or potentially lower).

  14. Galaxy disks do not need to survive in the L-CDM paradigm: the galaxy merger rate out to z\\sim1.5 from morpho-kinematic data

    CERN Document Server

    Puech, M; Hopkins, P F; Athanassoula, E; Flores, H; Rodrigues, M; Wang, J L; Yang, Y B

    2012-01-01

    About two-thirds of present-day, large galaxies are spirals such as the Milky Way or Andromeda, but the way their thin rotating disks formed remains uncertain. Observations have revealed that half of their progenitors, six billion years ago, had peculiar morphologies and/or kinematics, which exclude them from the Hubble sequence. Major mergers, i.e., fusions between galaxies of similar mass, are found to be the likeliest driver for such strong peculiarities. However, thin disks are fragile and easily destroyed by such violent collisions, which creates a critical tension between the observed fraction of thin disks and their survival within the L-CDM paradigm. Here we show that the observed high occurrence of mergers amongst their progenitors is only apparent and is resolved when using morpho-kinematic observations which are sensitive to all the phases of the merging process. This provides an original way of narrowing down observational estimates of the galaxy merger rate and leads to a perfect match with predi...

  15. THE GALEX/S{sup 4}G UV–IR COLOR–COLOR DIAGRAM: CATCHING SPIRAL GALAXIES AWAY FROM THE BLUE SEQUENCE

    Energy Technology Data Exchange (ETDEWEB)

    Bouquin, Alexandre Y. K.; Gil de Paz, Armando; Gallego, Jesús [Departamento de Astrofísica y CC. de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Boissier, Samuel [Aix Marseille Université, CNGRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Muñoz-Mateos, Juan-Carlos [European Southern Observatory, Casilla 19001, Santiago 19 (Chile); Sheth, Kartik [National Radio Astronomy Observatory/NAASC, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Zaritsky, Dennis [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Laine, Jarkko [Astronomy Division, Department of Physics, University of Oulu, P.O. Box 3000, FIN-90014 Oulu (Finland); Peletier, Reynier F. [Kapteyn Astronomical Institute, Postbus 800, NL-9700 AV Groningen (Netherlands); Röck, Benjamin R.; Knapen, Johan H., E-mail: abouquin@fis.ucm.es [Instituto de Astrofísica de Canarias, Vía Láctea, S/N, E-38205 La Laguna (Spain)

    2015-02-10

    We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6 μm photometry for >2000 galaxies, available for 90% of the S{sup 4}G sample. We find a very tight GALEX blue sequence (GBS) in the (FUV–NUV) versus (NUV–[3.6]) color–color diagram, which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale (τ) and a degeneracy between τ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the GALEX green valley (GGV). At the red end of the GBS, at (NUV–[3.6]) > 5, we find a wider GALEX red sequence (GRS) mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by M{sub [3.6]}) since both massive (M{sub ⋆}>10{sup 11}M{sub ⊙}) blue- and red-sequence galaxies are identified. The type that is proportionally more often found in the GGV is the S0-Sa’s, and most of these are located in high-density environments. We discuss evolutionary models of galaxies that show a rapid transition from the blue to the red sequence on a timescale of 10{sup 8} yr.

  16. The GALEX/S4G UV-IR color-color diagram: Catching spiral galaxies away from the Blue Sequence

    CERN Document Server

    Bouquin, Alexandre Y K; Boissier, Samuel; Muñoz-Mateos, Juan-Carlos; Sheth, Kartik; Zaritsky, Dennis; Laine, Jarkko; Gallego, Jesús; Peletier, Reynier F; Röck, Benjamin R; Knapen, Johan H

    2015-01-01

    We obtained GALEX FUV, NUV, and Spitzer/IRAC 3.6$\\mu$m photometry for > 2000 galaxies, available for 90% of the S4G sample. We find a very tight "GALEX Blue Sequence (GBS)" in the (FUV-NUV) versus (NUV-[3.6]) color-color diagram which is populated by irregular and spiral galaxies, and is mainly driven by changes in the formation timescale ($\\tau$) and a degeneracy between $\\tau$ and dust reddening. The tightness of the GBS provides an unprecedented way of identifying star-forming galaxies and objects that are just evolving to (or from) what we call the "GALEX Green Valley (GGV)". At the red end of the GBS, at (NUV-[3.6]) > 5, we find a wider "GALEX Red Sequence (GRS)" mostly populated by E/S0 galaxies that has a perpendicular slope to that of the GBS and of the optical red sequence. We find no such dichotomy in terms of stellar mass (measured by $\\rm{M}_{[3.6]}$), since both massive ($M_{\\star} > 10^{11} M_{\\odot}$) blue and red sequence galaxies are identified. The type that is proportionally more often foun...

  17. The Green Valley is a Red Herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies

    CERN Document Server

    Schawinski, Kevin; Simmons, Brooke D; Fortson, Lucy; Kaviraj, Sugata; Keel, William C; Lintott, Chris J; Masters, Karen L; Nichol, Robert C; Sarzi, Marc; Ramin,; Skibba,; Treister, Ezequiel; Willett, Kyle W; Wong, O Ivy; Yi, Sukyoung K

    2014-01-01

    We use SDSS+\\textit{GALEX}+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disk to spheroid and star formation is quenched rapidly. In contrast, the majority of blue star-forming galaxies have significant disks, and they retain their late-type morphologies as their star formation rates decline very slowly. We summarize a range of observations that lead to these conclusions, including UV-optical colours and halo masses, which both show a striking dependence on morphological type. We interpret these results in terms of the evolution of co...

  18. Evolving Galaxies in a Hierachical Universe

    Science.gov (United States)

    Hahn, Changhoon

    2017-01-01

    Observations of galaxies using large surveys (SDSS, COSMOS, PRIMUS, etc.) have firmly established a global view of galaxy properties out to z~1. Galaxies are broadly divided into two classes: blue, typically disk-like star forming galaxies and red, typically elliptical quiescent ones with little star formation. The star formation rates (SFR) and stellar masses of star forming galaxies form an empirical relationship referred to as the "star formation main sequence". Over cosmic time, this sequence undergoes significant decline in SFR and causes the overall cosmic star formation decline. Simultaneously, physical processes cause significant fractions of star forming galaxies to "quench" their star formation. Hierarchical structure formation and cosmological models provide precise predictions of the evolution of the underying dark matter, which serve as the foundation for these detailed trends and their evolution. Whatever trends we observe in galaxy properties can be interpreted within the narrative of the underlying dark matter and halo occupation framework. More importantly, through careful statistical treatment and precise measurements, this connection can be utilized to better constrain and understand key elements of galaxy evolution. In this spirit, for my dissertation I connect observations of evolving galaxy properties to the framework of the hierarchical Universe and use it to better understand physical processes responsible for the cessation of star formation in galaxies. For instance, through this approach, I constrain the quenching timescale of central galaxies and find that they are significantly longer than the quenching timescale of satellite galaxies.

  19. New Light in Star-Forming Dwarf Galaxies: The PMAS Integral Field View of the Blue Compact Dwarf Galaxy Mrk 409

    CERN Document Server

    Cairos, L M; Papaderos, P; Kehrig, C; Weilbacher, P; Roth, M M; Zurita, C

    2009-01-01

    We present an integral field spectroscopic study of the central 2x2 kpc^2 of the blue compact dwarf galaxy Mrk 409, observed with the Potsdam MultiAperture Spectrophotometer. This study focuses on the morphology, two-dimensional chemical abundance pattern, excitation properties and kinematics of the ionized interstellar medium in the starburst component. We also investigate the nature of the extended ring of ionized gas emission surrounding the bright nuclear starburst region of Mrk 409. PMAS spectra of selected regions along the ring, interpreted with evolutionary and population synthesis models, indicate that their ionized emission is mainly due to a young stellar population with a total mass of ~1.5x10^6 M_sun, which started forming almost coevally ~10 Myr ago. This stellar component is likely confined to the collisional interface of a spherically expanding, starburst-driven super-bubble with denser, swept-up ambient gas, ~600 pc away from the central starburst nucleus. The spectroscopic properties of the ...

  20. VLT/X-shooter observations of blue compact galaxies Haro 11 and ESO 338-IG 004

    CERN Document Server

    Guseva, N G; Fricke, K J; Henkel, C

    2012-01-01

    (abridged) Strongly star-forming galaxies of subsolar metallicities are typical of the high-redshift universe. Here we therefore provide accurate data for two low-z analogs, the well-known low-metallicity emission-line galaxies Haro 11 and ESO 338-IG 004. On the basis of Very Large Telescope/X-shooter spectroscopic observations in the wavelength range 3000-24000\\AA, we use standard direct methods to derive physical conditions and element abundances. Furthermore, we use X-shooter data together with Spitzer observations in the mid-infrared range to attempt to find hidden star formation. We derive interstellar oxygen abundances of 12 + log O/H = 8.33+/-0.01, 8.10+/-0.04, and 7.89+/-0.01 in the two HII regions B and C of Haro 11 and in ESO 338-IG 004, respectively. The observed fluxes of the hydrogen lines correspond to the theoretical recombination values after correction for extinction with a single value of the extinction coefficient C(Hbeta) across the entire wavelength range from the near-ultraviolet to the ...